I tow four down rather than a dolly and used a
Dual Hitch Receiver. It has a higher weight rating than my hitch and tow bar so a bit of overkill and might be a bit outside of your budget. I needed the drop to line up the tow bar to the car base plate. Worked great for 10,000 miles towing with a bike rack. Changed from a Accord to a CRV with so I no long need the drop and the bike rack is now on the back of the CRV. I did cut back the rack a bit so it was closer to the coach to clear the vertical pivot point of the tow bar.
