I badly scratched up my Sea & Sea dome port (it's acrylic) while diving at Cocos and Malpelo. Lots of current and lots of rock is a bad combination for a housing with a big dome port. A couple of fairly deep scratches (you could easily feel them with your finger) and some shallower ones (you could feel them with you finger-nail).
After doing some research, including some older threads on this board, I decided to try the Micro-Mesh NC-78-1 ACRYLIC RESTORAL KIT (Micro-Mesh) . It's made fo