I found that the fiberglass is often too thick for the tinnerman nuts to to be installed.
It seems many badges and emblems have "posts" that are only long enough for the them to be installed in sheet metal.
I modified a cheap flat blade wood drill to cut a counterbore into the fiberglass on the inside. The counterbore has to be big enough to allow the full length of the tinnerman nut to be flat against the bottom of the counterbore.
This worked really nice but don't over do to !! Otherwise you could have a huge hole to fill ! See drawing below...........Bruce