Step 5: Adding a brace to make a snug fit: drilling
The diameter of the small end of the hood is almost perfectly suited to snug onto the ring around my camera's lens. But not quite. I decided on attaching a small cable tie to brace it. It's the best solution I could come up with (having tried a bit of gaffer's tape to reduce the diameter inside the hood, but ruling that to be too impermanent).
In these next few pics, I'm drilling a hole to mount the tie, then using a small square needle file to create a channel for the zip tie to rest in. More on why in the next slides.
If you don't have access to a drill, you can find another way to put a hole in the relatively soft PVC: an awl (such as you'd find on a Swiss Army Knife) would work, or a soldering iron would melt a neat hole through (and stink your workshop up).