Actually Don, we may have side tracked a bit here, but the CG shift we are discussing is static, no dynamic loading, that would be indeed a difficult task to determine.
The bottom line is the load applied to the rear axle is the difference of the loaded and unloaded rear axle, and that is what the trailer is putting on the trucks rear axle. I suppose that the true pin wt could be calculated a few ways but not very helpful in regards to what loads we have on the truck.
Ok, now my head hurts!!
Gotta go fix my broken slideout!
Cheers,
Bill