Jack
Actually I was a little surprised it was an issue with you given your trailer size and that the f150 is a similar tv to my Titan I.e half ton etc. on the other hand, I have a buddy with a 16ft Casita he pulls behind a Chevy 300o size van and he seems to need it. That said, I guess I always figured the shorter length, less weight, and single axle were contributing factors. In that case, it makes sense to me that you may have more issues than I. Also, those double axles of mine are still set pretty far back and it makes sense to me that an asymmetrical set-up like that would be prone to less sway in that it will resist pivoting more-so. No engineering knowledge here, just my experience n canoes and kayaks . I've survived some pretty nasty cross winds in it, however. I've always felt that I should mount mine, though, before the next major cross country trip. I Do notice it if I set the hitch one link higher.
Rick