Is there a Motorhome size restriction?

Yes

I don't believe three is a restriction.

I don't think so

Not that I'm aware of. The spaces closet to River with hook ups might not be convinient for all sizes, but there's a section at the top of the hill that is specifically for RVs that looked like it fit and has many different sizes using them.

I don't think so. But i honestly don't know for sure