Sorry this is a bit late
Hi,
I have an Opemus 3 enlarger with 70mm and 35mm lenses, and 35mm and medium format negative carriers.
I removed the red glass from its holder, and perched multigrade filters there instead, using an inline switch to control exposures. It worked fine.
I also upgraded to a Nikkor lens, it cost £90 about twenty years ago, but was not as sharp as the original lens and I sold it for a lot less.
The whole kit is now surplus to requirement: enlarger in it's original suitcase style box, and all developing equipment for prints and film.
If anyone is interested and wants to collect from Glasgow, let me know.