I didn’t ask that specific question (using a aftermarket plate with an optic that the factory plate set supported) when I was told aftermarket plates were allowed. But, I don’t see it ever being an issue.
Milled slides, No.
Rear dovetail mounts, No.
Using a MOS gun without an optic, No.
The above was from a discussion with GSSF staff before the rules were released.
FWIW, I’ve ran a FCD mount with a 507C at 5 matches this year.
Over the recent years Glock has changed standard sight heights. The standard used to be 6.5mm rear with 4.1mm fronts. Now most ship with 6.1mm rear and 4.1mm fronts. That goes for GNS night sights or polys. Ameriglo Bolds generally ship with .200 front but I have found the .180 to be best for me in conjunction with the .276 rear.