Another technique that works well on broken buttplates and recoil pads is to epoxy the broken plate to one of the thin black plastic or rubber spacers offered by the likes of Brownell's. Another 1/16" to 1/8" inch added shouldn't affect much as to dimensions, yet affords a platform to epoxy to.
I was once given a brand new Red Head pad (i.e. not ground down)that somehow got cracked clear through the black rubber backer. With this method, the repair was virtually invisible, and stronger in that the glue line was not only holding at the crack but bonding with the full pad surface.
Robt.
