Step 6: glue the LED's
the glue is all we are using to hold down the LED's. it seems tough and durable to me, but if you are worried the alternative is for you to drill 2 holes in the heatsink for each of the LED's (matching the cutouts in the star), and bolt them down with 4-40 size nylon machine screws. (or 3mm size). you can get nylon machine screws from www.mcmaster.com
1) do not get any glue on the LED lens. some glues (like silicone) you can get off the lens after it dries.
2) make sure the glue can handle 80-100 degrees celcius. (don't use hot-melt glue!). make sure it is waterproof (don't use superglue / cyanoacrylate)
3) i used silicone, but if i do it again i will try epoxy instead. the silicone does not flow by itself, so it is hard to get it to fully cover the LED (in order to have a submersible lamp). with epoxy you can dispense it with a syringe and accurately get it everywhere but the lens. smearing the silicone around is messy.
4) after pouring the glue, press the lens holders into place on top of the led's