So just drill the holes, pin and fill the steel voids with epoxy and not worry about coming loose or shifting?Pins or sex-bolts.
Sure , but some light weight wood would do same much faster and cheaperEpoxy will do it fine. If you wanted to you could fill the voids first. Use PC7 or a putty type epoxy. Put the knife down on a sheet of waxed paper. Put the epoxy in the voids and smooth it out. Let cure and then file/sand the excess flush. Mount the scales as normal from there.
Balsa is good. Even foamed plastics work great. Easy to shape and glue.Sure , but some light weight wood would do same much faster and cheaper