I don't have a WD hitch. TT is only 4000lbs +/_ . I do have a anti-sway bar. We tested it today with my GF in the back and made a couple of 90 degree turns. It comes close to the sway bar on a 90degree turn but misses it by 1/2". The good thing about custom building is you may be able to work around your hitch connections. I thought about putting the one bracket in question ( at the sway bar ) on the inside of the frame instead of outside but it does not appear necessary. A bigger TT may have even more flexibility on design. My tongue area is small and tight.
On the aerodynamics....I don't think that could get any worse :)
