Here's the final answer...
Don't tow your dinghy.
If it's anything more than across a calm lake, towing a dinghy will only result in dissapointment.
It will, however, give you an excuse to go buy a NEW dinghy, so if that's what you're looking for...
S/V Baloo, lying San Carlos, Sonora, Mexico
I have to disagree -- sometimes dinghies must be towed. Some of us sail boats without enough deck space for a dink, and I hate inflatables! I've towed dinghies for many miles in many kinds of weather. In bad weather I would rather tie the dink up close to the stern with chafing gear.
I have thought about making a tight-fitting cover for the dinghy, ... with a ridgepole (probably mast) stem to stern underneath, It should keep water out. Anyone try that?