I have an M5-235C with 1090 hours since new. All good compressions, an oil catch bottle on the breather and always a clean belly. My oil level seems to like 7.5 Qts. I can add more but it quickly settles right back to 7.5 Qts. and stays there. There's a very small amount of oil in the catch bottle and no leaks. What's the norm for these???

I would say there is no norm. Each one is different. It's when the consumption rate changes that you need to start looking for problems.

Mine is very similar. Some previous owner actually stamped a dimple, slightly lower than the 9 quart mark, where the oil level seems to stabilize.

Mine runs about a half an inch below the 9 quart mark.

Same for me. Just below 9.

Same here. Levels out at approx. 7.5 to 8
MX-7 IO540

Oil catch bottle? Is that something that I can get from Maule, or did you rig something up on your own? Can you provide a picture? I hate cleaning the belly of my plane because the oil residue makes it such a nasty job. I hate it, but I do it regularly. Catching some of the overflow from the breather tube would certainly make the belly cleaning job easier!