alan,
I don't remember who first employed the technique, but it has been discussed in a number of threads. I "think" I recall it being initiated on a MKII trunk lid, which required removing the aluminum liner. Then the recess on the inside surface of the trunk lid was filled (again, I don't remember if is was 'glassed w/cloth or mat, or simply packed w/high-strength filler), & after it cured, the offending "nipple" was ground off the outside. Prep the exterior surface appropriately.
Low-tech, but very simple & practical. Kinda reminds me of the sculptor explaining how easy it was to create a work of art:
1) Find a big rock
2) Using hammer & chisel, remove everything that doesn't look like a statue
Easy, right?
Best,
Matt