on buttons position and on Teflon feet
yeah, switches could be anywhere, right. But it doesn't matter much. My point was about leverage: the farther you press from a pivot point of that springy warped cover, the less is your effort. A different approach to a complete cutting out button covers would be "unwarping" them like in positions closer to the scrollwheel where they have bent inside profiles which strengthens them and makes harder to bend/push.
On teflon: that's right, the real good, almost unscratchable (means: durable, and sliding freely over abrasive dust & dirt on hard grained polypropilene/teflon/milky glass mats for years) teflon is expensive: e.g., just three 0.09 mm thick 4"x3/4" strips of 3M Teflon 63 PTFE tape with acrylic (semi-permanent) adhesive are about $6. But guess what: they use it in lots of electronic components like (big) electrolythic capacitors, (big) coils, wire harnesses, quality/power/high-voltage multiwire cables. Now find some 3rd party acrylic not-so-thick glue, and you are all set after some autopsies of your spare electronic components. Hint: a good high quality teflon you're looking for won't be cut easily by ordinary scissors, only a very sharp serrated pro barber tool can do the job. Or a special hardened punch.
I just got more hints about teflon sources. Like there are reports of using slivers from so called "nonstick" frying pans. Here, again, the results are mixed: low-quality low priced plastic something Chinese put on their cheapo frying pans is useless for your mouse, but who would destroy a genuine high quality Teflon coat from a >$80 worth good brand kitchenware?