I respectfully suggest you think about that for a second. How can towing something not slow you down?? And if there was so little stress on the dinghy, how is it that so many are lost or discovered floating at sea minus their D-rings? I personally have lost one and my father alone has found 2 at sea in the last 5 years.
My boat cruises at 7-8 knots; when I have to tow the dinghy it's more like 6-7 knots and there is no way I can pull the dinghy towards the boat by hand at that speed.
I respectfully suggest you read what I wrote and try it. My airfloor inflatable is 10'2" long and it has a 9.8 Hp motor. I tow it at 6.5-7 knots. I can hold the tow line between my forefinger and thumb. If I pay out another 6-10 feet of tow line, I can barely hold on with two hands. Try it, and you'll see what I meant when I suggested there are some dim bulbs losing dinghies for no reason.