Aasem I agree that you shouldn't loose a dinghy if made fast right and from my experience the best tow-length is riding "off" your own boat wake as close as possible to one or the other side of the transom, but never in the center as explained by 'Aasem'. Longer lines give a chance for 'dirty' water to throw the dinghy of the S/V's wake (I speak from experience, tried it both ways)
I'm always able to direct hand pull my dinghy closer to the aft of the boat without resorting to a winch and that is over 350lbs of dinghy. (finger & thumb is questionable, hand yes)
I disagree that it doesn't really cause any friction riding down the wake, it will still slow me down by more than 1 knt.
We'll find out again this weekend with strong winds (25mph) when pulling her for 20 miles.