Tie the rope around the inflatible pilot's waist and tell em to hang on
Seriously though, it would seem like the transom would be the logical
place to tie the rope if anyplace will work at all. The transom has to
be strong enough to deal with the force and weight of the engine
pushing the boat. I doubt anything else on an inflatable is built as
strongly. Plus the transom will be getting more force from being
pushed forward by the engine, so maybe some pull from the skier will
equalize that out a bit (not sure on that though though).