IIRC, even the games themselves (even just looking at the Japanese versions) aren't consistent. I'd say let's go with whatever spacing's been used in the most recent of the classic series (which'd prolly be 10).
Ah I see, didn't know underscores came later. Hmm, this is gonna be a lot of work for someone if we're to use implications for every single robot master... there's 88 of them, I think?
This seems like the best one to BUMP, but I just got access to the "Robot Master Field Guide" (ISBN 9-781926-778198). For all *man Masters, they are rendered as "___ Man". But, bear in mind, this is going with English/US names, so they're Treble and Bass.