I think you have to be more careful about wind strength towing an inflatable(especially downwind). I have a good friends who's inflatable flipped while towing in high winds(gusts maybe 40k or so) Unfortuantely, the motor was on the inflatable as he only had a few miles to go....

I don't see any advantage to a long painter with an inflatable. The least amount of drag will be snubbed up pretty close with an inflatable, at least from what I see. The ones towed far back usually have their bows pointed skyward.