The keyboard is designed with three main goals:

as quiet as possible, given it's low profile, with priority on minimising the higher pitches
should be designed to be bottomed out on each keystroke
have the shortest and lightest stroke possible

Combined, it should allow the user to type as quick or hard as they would like, hopefully facilitating quicker typing, whilst still being usable in an office environment.

The short stroke and ultra light springs takes a little while to get used too, a day or so of typing, then back to your usual WPM.

If you want to do this yourself, be prepared to spend between 8 and 14 hours. It depends on a lot of factors, like if you batch lube all of the springs, or if you prefer brushing them, if you have steady hands that allow you to tape each side of the top housing in one go, or if it takes several.

https://www.youtube.com/watch?v=W6-uYGbxBq4

Supplies

Materials:

PE foam, 1mm thick
silicone sheet, 0.5mm thick
preferably some new switches, these are choc v1 purpz
switch / keyboard grease

Tools:

a mask
leather hole punch at 2.5mm and 5mm
scalpel or a razor blade
ruler, metal or plastic
regular switch-lubing kit (brush, fine tweezers, switch puller, etc)
recommend you use an ESD wrist strap

Step 1: Cut PE Foam to Size

Follow the official ZSA tutorial for disassembly: https://www.zsa.io/voyager/teardown

If you have an ESD wrist strap and/or mask, now is the time to put it on. A mask will stop you from accidentally inhaling any tiny plastics.

Trace the green "mid-plate", making sure you draw or make a mark on where the screw holes are. I recommend cutting across the two screw holes in the top, as shown. It provides better circuit coverage that way.

Once you've traced it, cut it.

When reassembling the board, make sure you tighten each screw just a little bit until all of them are reasonably tight. You will have increased the pressure in the board slightly, so to avoid any single part of your circuit board taking more force than it needs to, be slow, incrementally tighten screws. Is it really going to matter? Probably not, but better safe than sorry.

Step 2: Disassemble Switches

Yep.

You stick your pliers in and lift the tab to release each side, being careful not to break off the tabs.

There are plenty of guides already on this, so I'm not going to repeat all the details here.

Step 3: Lube the Springs and Stems

Yep.

Lube.

If you haven't done this before, I'd advise at least trying one normal set before following this considerably more extreme tutorial.

Step 4: Tape the Top Housing

Place tape on a cutting surface and cut several 0.7mm strips. You need to be between 0.5 and 1.2mm, more or less is going to change the feel of the switch significantly.

Simply take your razor and run it along the length of the tape, using your ruler as a guide. I used a scalpel / craft knife, but you should use whatever tool you are the most precise with. While it's not exactly free hand cutting, it still requires a great deal of precision for consistent switch feel.

I tend to stick it to the outside of the top housing and then roll it into the centre of the "donut". It's by no means a secret technique, it's just the most consistent I've found. If you find a better way, please let me know.

Snip the excess to a length of no more than double the top housing tabs, so roughly 5mm total. If there's too much you'll get extra mushiness from a completely depressed switch and inconsistent press lengths.

This is the most critical part of the mod, as inconsistency will significantly vary the feel of your switches. If you have a few bad switches, doing them as required is fine, but give them a week to actually break in before you decide they're bad.

Step 5: Punch and Fit the Washers

Cut the outer diameter at 5mm, and inner diameter at 2.5mm. See the Kailh drawings attached.

Because the internal space is exactly 5mm, to allow for some tolerance with the internal diameter being slightly off centre, I would advise chopping off a tiny amount from the end, somewhere between 0.3mm and 0.6mm, as shown. You can also cut the outer diameter at 4.5, but I prefer more surface area. If I had a hole punch at 6mm or more, I would have used that instead.

Sourcing the materials for this, especially with a silicone with a rated hardness is going to take a bit of time. Do not go with anything over 0.5mm, the shortness of the stroke is already very significant with 0.5, in hindsight something around 0.4 or 0.3 would have been perfect.

I personally decided to scuff up my silicone by using sandpaper to reduce the tack noise on release after being fully depressed. I used 80 grit, but 160 to 240, maybe something in the 500's would have been a better choice, as the deep scratches give less strength to the material and becomes harder to work with.

Step 6: Assemble Switch and Keyboard

I start with the stem and the top housing, then attach the spring to it, then the bottom housing to press it and click it back together. The reason I start with the top stem is because the tape will normally interfere with it if they are curved "inwards", so it's the hardest part. Trying to keep the rest of the switch together while fitting these two parts together can be a bit tricky otherwise.

Step 7: Bonus; Things I Tried

I tried a full size silicone bottom to the switches, didn't work as well as I thought it was. The noise reduction is negligible in comparison to the round washer. The internal diameter is absolutely critical however: in the 5 prototype washers I made, the most consistent key presses that didn't stick on full depression were the ones with better cut centres.

I tried an external O-ring, but it didn't line up with the new keycaps I had due to the ripples. I even tried cutting one to the size of the stem with roughly a mil offset all the way around as a sort of bumper that just loosely sat on the switch, and they both helped, but the washer was a better solution for both the sound profile and for a lack of rattling parts.

The tape acts as a sort of wear plate for the stem to pass over, as well as tightening the tolerances on either side such that the stem is will tilt to either side when pressed off-centre, scraping the walls of the top housing. I've tried every size from the full width of the sides, to a 0.3mm strip, and I think between 1.1mm and 0.6mm it will provide the best actuation without too much friction on the stem. If you go above 2mm, you start to get sticking keys that take a long time to return after being depressed.

I didn't believe that the tape mod was really that effective at reducing noise, but after having done it, I recommend it. I would go as far as to say it helps more than lubing does, but obviously both are important. No point having a wear plate without lubrication.

The last image shows three other variations I had made and they demonstrate very clearly that the spring transfers a lot of energy into the bottom housing. Ideally the spring when fully compressed is around 2mm long, and the stem should have a recess to house the compressed spring, meaning the stem itself should be hitting the base. In reality however, even when I give it 1.5mm bumpers on either side to stop the stem, the central 0.5mm washer that I ended up using is still quieter. The stroke of the 1.5mm bumpers is obviously much much shorter and it certainly stops the stem before the spring is fully compressed. Why this works the way it works is completely bewildering, I would have assumed bumpers would have been superior, but even when using a central washer bumper that allows the spring to sit in the middle of it, there's still more noise than a washer sitting between the base and the spring. It's not simply that the centre of the stem transfers more noise, it's definitely the spring.