Attaching transom tie-downs to the ski tow eye seems like a pretty horrible idea to me. Those things aren't even up to pulling tubes (see all the topics this season about people yanking ski tow eyes out from pulling towables), so using them to anchor your boat to your trailer can't be a good idea. Ski eyes are usually attached to a thick area of fiberglass with some sort of backer board (often 1/2" plywood) while the transom eyes are thru-bolted through 2" of plywood sandwiched with fiberglass.
The shock on the transom straps (e.g., when hitting a bump) would only be magnified if they were slack, so tighter makes more sense to me.
If it were my boat, I'd move the transom eyes a bit outboard, fill the old holes properly and be done with it.