I have an Opemus 5A. It has a negative carrier with plain glass, which is no good, Newton rings are a problem. Thus I modified it by using the anti-Newton half of a 6x6 GePe AN slide frame (which I tooled a little to make it fit). :) This seems to work, but a real anti-Newton glass might be better.
So I wonder if anyone here knows whether the glasses for Opemus 6 also fit Opemus 5A negative carrier??

The glass will also fit your enlarger, the negative carriers of the 5 and the 6 are identical in size.