1. What is your loaded TW?
2. What is the rating on your WDH?
I assume that #2 is greater than #1.
But if these 2 numbers are too close together, the WD bars are too easily flexed, and this can lead to that bouncy ride (known as "porpoising", as it's the center coupler area that is actually bouncing up and down from those "spring" bars).
I had this problem when I was using a 400 lbs rated WDH to tow our previous popup camper at 375 lbs TW. I needed the WDH because we were using a minivan. Crank it down hard enough to get the loading right, and it was bouncy. Don't crank it down enough, and the front loading was too light. The solution was to lighten the TW a good bit, and rely on the friction sway controller. Not a great solution, but it worked.
thebrakeman ('70), DW ('71), DD ('99), DD ('01), DD ('05)
2004 Surveyor SV261T (UltraLite Bunkhouse Hybrid)
2006 Mercury Mountaineer V8 AWD Premier
Equal-i-zer WDH (10k), Prodigy Brake Controller