Since CO has been becoming more popular, I've looked at converting my back up G17 into a CO gun.
I've read a bunch of earlier posts on the topic, including the multi-brief from Feb. 2016.
Does that still hold true?
"Note that many Production division guns can be easily modified to compete in Carry Optics as well as Production, but be cautious with the modifications you make, as many will render your Production gun illegal for that division. You can mill the slide of a production legal gun to install an optic, and replace the optic with a filler plate for competition in Production without risk."