Ok, as promissed, I have fired 50+ rounds w/o a single observable change in the button fix.
I have also made the dimensional measurements for the button inserts:
ID ~ 1.5 mm
OD ~ 3.0 mm
Height ~ 2.5 mm original cut from pen ink tube melted down from both cut ends to ~ 2.0 mm
These dimensions are currently providing extremely reliable index finger & thumb activation, while maintaining consistent resistance to activation via flat surface rubbing.
Hope this helps! (Told ya it would be short this time!)