Jared,
No doubt, Barn O is 100% correct that a 35 is more maneuverable. But, our bus is 45' long, and a solid 13' tall. We have gotten it into some incredibly tight spots, and gotten it back out. So to us, 40' is a sports car. But then again, a 35 would be even better. I haven't seen too many signs restricting lengths. It is often a matter of whether you can get safely in and out.
God bless,
John