5th wheelers size and frequent relocation/campsite fit size?

OP here: Everybody--thanks for all the great info. That answers most of my questions.

Question: is there a regulation size/length for federal and state camp sites? I assume states would vary, but federal would be the same, but you never know.

From you responses, given that I will be mainly in federal and state campgrounds, not private, it sounds like there there are few sites for 40 footers.

From your responses, it sounds like I want an aerodynamic nose, and maybe keep it under 35 to keep up a maximum of sites available.