Weights and aerodynamics - where do I post and query?

Only way to tell what your RV weighs is get it weighed at a scale.
Lots of info here on Air Tabs and other improvements on RV.NET.
Here is one thread in Truck Camper forum. It shows making a air foil to stop wind noise between and cab over and truck cab. I used Air Tabs to stop noise from wind in the cab over/cab area and cab side windows. Helped a lot. I have Air Tabs around rear of my MH. Helps with handling. But cannot tell if it helped fuel mileage.