Luger Carbine hanger & serial number

Making a carbine with 16 inch barrel. If I weld a hanger in the normal place on the luger, the serial number will be destroyed. It is a 1920 commercial. Is it legal to destroy the serial number if you restamp the serial number in a different place? Or would it be better to attach the fore stock to the barrel and cut out the wood to allow the short recoil? Any ideas would be appreciated.