What JRY309 said. Also, are the screw-in heads you have manufactured that way or are they just glue-ons with alminum adapters installed? You could switch out the adapters.
Also following JRY309 and tapping the back, you could just use a machine screw and washers or nuts on the back side of the insert instead of buying PDP components - get your weight set and lock-tite it in then glue in the insert.
Its all about creativity and imagination. This is the kind of stuff that led to the product guys are selling.
Good Luck!
And tell us what you ended up doing. We all can learn.
BobW