Since it is raining here, I decided to install the clamp. I used wellnuts as this is what's available at the local hardware store.
1. Locate centerlines:
Apply blue tape on the clamp edge that will be by the roll bar, head liner and roll bar.
With a pen, mark the centerline (this is lined up with the existing hole in the roll bar center the clamp and mark the location of the hole.
Locate centerline of the clamp and mark with the pencil.
2. Place the clamp and line up the centerline marks. Taped in place.
3. Followed jpryor27's method on marking the hole locations. For my hardtop and clamp, the hole centerlines were ~4" apart and ~3/4" from the edge, your's maybe different.
4. Drilled pilot hole. I wrapped a painters tape around the drill bit as I guide how deep to drill (picture below).
5. Using a sharp blade, removed headliner material around the pilot hole (about 5/8" diameter).
6. Drill the hole for the nut. Firmly hold the drill, slowly drill and do not be trigger happy. Not probably needed, I progressively used bigger bits until the final one (5/8" diameter).
7. Installed nut without glue to confirm fit.
8. Installed the bracket and tighten. No more bulge.
I did all the drilling while the hard top was installed.
2005 Storm Ti, LSS, Touring.
1969 Karmann Ghia Convertible.