In addition to the mooring eyelet, and rope tie down holes maybe not being strong enough (the manual recommends against using them), they would put the tow rope too low in the water. That makes the tube try to submarine, gives the riders a rough, wet, and unpleasant ride, and puts more stress on the ski. I've seen people tow from the grab handle, but that is an accident waiting to happen.
Best bet is to install a tow eye just below the handle. Something like this, but I'd make the backing plate bigger to distribute the stress:
Stainless Steel 3/8" Marine Bow/ Stern Eye Boat Trailer Tow Ring Hook 4-5/8" | eBay
Here is what one guy did to get the rope even higher. He claims it works great. It uses the tow hook he installed under the seat, and the rope holes on the platform for support. It looks like it would make the ski unstable to me. I think just using a hook just below the handle would be safer, but it may give you some ideas: