Scary Handling Problem

Had the same issue quite a few years ago towing a CJ7 with a fairly short class C. Take a look at your wheelbase length on your rig vs how much length hangs beyond the rear wheels. If the overhang beyond the rear wheels is excessive (anything over 1/3 the overall length of your rig) that could be the issue in a nutshell. A tough problem to overcome "inexpensive." The tail ends up wagging the dog due to the amount of force it takes to move the front wheels of the toad. On my fourth rig and I tow a grand cherokee right now and that is the first thing I now check before buying a new rig. Sorry this may not solve your issue but something to check.