The same logic (or lack there of) applies to MH lengths. Ours is a 39S model, but the mfg's web site says it's 39' 8" long. Considering how mfgs like to inflate things for marketing purposes, you would think they'd call it a 40' MH since it's closer to 40' than it is to 39'.
Someday when I'm really out of things to do, I guess I'll measure it to see what the body length is vs. bumper to bumper. Maybe, front bumper to the rear of the ladder going up the back since it sticks out past the rear bumper. And of course I did add a flag mount to the ladder which sticks out another 6". I wonder which length to give next time we make an RV park reservation? I think I need to take a nap and think about this for a while.
This post is subject to revision when I wake up.
Bill