Just my 2 cents as an owner of these:
I received the Thumbstick covers the other day and they feel and look great.
Sadly, the issue I have with them is enough for me to not use them. I cannot press the X button or the Down button on the D-Pad. (Both needed for Destiny remote play)
The analog sticks are too high after installing your caps and it makes games harder to play when you need those two buttons.
It's a shame because they feel great as analog sticks, I just can't see myself actually using them since those two buttons are near impossible to press now.
Just thought I would give feedback. Build quality and everything is great. But the way they sit on the vita make them not work well for me. I see others are happy, so It's probably my issue.
If the top part of your caps were overlapping the base of the cap where it snaps onto the vita I think the issue would be solved. Keep me posted if you improve/change the design.