Filling Roof Rack Caprice Wagon

If anyone has any tips on what they used or pics that would be great. I actually bought the fiberglass fillers and attempted to get them to work. They fit like garbage and wont fit flush with the roof. Any pics from a 1991-1996 Caprice, Roadmaster, or Cruiser wagon might help me out.

I actually made my own. It took a little bit of time but it layed down three to four layers of masking tape in the groove and when waxed the tape with a paste wax. Then began laying down a layer of fiberglass mat and resin. I did about four layers then drilled holes and installed 1/4" bolts down through the holes. Then ifinish adding a few more layers of mat and resin and finished the last bit with duraglass. They popped back out fairly easy and once the masking tape was removed it left the gap needed for primer and paint. Hope this helps you out and I'll see if I have any in progress pics.