There's an easier, less invasive way.
Get a can of Johnson's Paste Wax or even some shoe polish wax. NOT CAR WAX.
Liberally coat the screws and the inside of the butt plate with a thick coat of wax. Don't wipe it off.
Mix up some 5 minute epoxy glue and pack some into the holes. Work fast, and put the butt plate on, then screw the screws in until they almost start to turn too far, then let the epoxy cure for 20 minutes or so.
Carefully remove the screws and clean up any excess epoxy and clean the wax off everything.
Let the epoxy fully cure and reassemble.
The holes will be repaired and will be even stronger then when new, and there'll be no sign they were ever stripped.