We pulled our Koala with a WDH, no issues at all.
This being said, "bolt to frame" vs "crossmember" talk is kind of trumped up armchair engineering. What do people think a hitch bolted, or welded, to both frame rails is? Uh-huh, it's a crossmember.
All a WD hitch is is effectively a spring that, in applying upward force, relieves weight on the rear axle and "distributes" it to the tow vehicle front axle and the trailer axles. One other side effect is that a WD hitch reduces effective tongue weight as a result. OP, with < 300 lbs on the tongue, over-adjustment of the WD bars can cause some driveability issues, mainly rear traction.