Ground clearance for dinghy

We tow a Ford Focus behind a 30 ft. Class C. Clearance of the Focus isn't the problem but the rather low point of the Blue Ox tow bar hook-ups on the front of the Focus is a problem because I had to drop the hitch on the rear of the motorhome with a 4 in. drop hitch to be level. Therefore the hitch on the motor home drags easily because that's the lowest point; not the towed Focus. So, where the hook-up points on the dinghy is, is crucial. Blue Ox tells you how many inches high it is.