Ok, I checked out the grooves with good illumination and a larger screwdriver. The stbd hull's groove is cracked nearly three quarters of its length. Gary did indeed make a good effort to open the crack and epoxy it, but it has broken open again. A smaller(shorter) crack is visible in the port hull, which hasn't been repaired. I really don't think I can easily and sufficiently reinforce this groove to the point that it will reliably hold in a bolt rope. When I pry gently with the screwdriver, I can see the cracks open up, as well as noticible flexing of the hulls in the vicinity of the groove. In my opinion, any successful repair of this design would need to occur from the inside, which seems substantially more work.
I found a couple of lengths of alum C channel from a SC20 that seem stout enough to stand up to the loads. I'm currently drawn to attaching these to a filled and glassed over groove. So unless someone here talks me into something else, my next questions are:
If I fill the groove with West high densitity filler and tape over the groove, would that be solid enough to attach the track with #10 x 1" self tapping screws? (I expect to epoxy the track down as well). Or should I embed nuts in the groove when filling? If so, I'm gonna have to locate them accurately, probably with the track and some bolts. What can I spray/coat the screws with to insure that they'll release from the epoxy?
Thanks for all the input guys, my thinking has gone thru a fair evolution since the beginning of this thread. I'm excited to beef this boat up enough to stand up to the abuse I'm sure to give it.

Dave