[G.R.]

I had 1/4" by 6" plate welded to the frame rails under the seats about in mid shoulder/hip line. Drilled through the seat bottom and plate there is just enough room under both seats to fish the strap and mounting plate then bolted them in with grade 8 bolts and nylocks. Sounds easy but is a pain because I had to pull them a couple of times and reinstall after making length adjustments on the strap. My seat belts were a problem as there was no possible way to weld in a plate due to the frame design, so I used about 1/4" x 6'' x 10'' plate for each side of the belt bonded to the cockpit tub with epoxy and then drilled holes for the belt attachments. Only way I could figure out how to do it and have it secure, figured if it came to "down" it would have to tear through 1/4'' of fibreglas the length of the plate before letting go. I hope.
My shoulder belts are "Y" type and there were attachment points built into the frame for this type and they come up through the trunk deck.