According to the Reese "Weight-Distributing Hitch Selector," the 1200 WD
Hitch is suitable for tongue + rear-of-tow vehicle cargo loads of
600-1200#.
If it is too bouncy anyway, you can get lighter leveling (spring) bars
from Reese for 400-800# or even 200-600#.
Having too stiff bars will put too much load on the trailer suspension
(and of course, frame) when you drive into dips like crossing gutters
going into gas stations.
Instead of spring bars what is really needed is a spring element with a
much lower spring rate so that the bar loading is more nearly constant,
like a gas spring (accumulator), no matter what the vertical angle
between the tow vehicle and the trailer. But of course that would be much
more expensive.
Al