Thats the type of frame I want Daibheid. I saw one of X-ribs towing frames at the boat show and that was bolted entirely to the transom like yours. I think Ribcrafts towing frames are the same and only bolt to the transom too.
Is yours a 1.5" or 2" dia tube? I'd phone ribcraft, it may be that your frame is basically the same as their towing frames just without the eye at the top....
Any chance you could post some pics of it. Espically where the Fwd frame comes back into ther transom......I'm looking to get one made up locally to same a few ús.