The door is 1-3/4" thick with a foam interior. The hole is 1/2" diameter and extends the full thickness of the door. (It was made to accommodate a pushbutton deadbolt lock.)
Bondo seems to be the choice for taking care of the steel faces, but I'm looking for suggestions for the cavity between the steel faces. I never used Bondo before, so I don't know what kind of backing it needs. Maybe a simple wood dowel, just slightly shorter that 1-3/4" would be okay.
Thanks,
R1