On a GSG 1911,... DO NOT DO THIS !!!!
They can barely stand the recoil of the .22, I have had one I owned crack and had 2 others from other people cross the bench all cracked or failing from only .22 The GSG also has had some special provisions made to the frame for that dedicated upper. They are NOT within normal 1911 specs,...just try and upgrade internals or grip safety and you will know what I'm saying.
These frames are made of Alumi-something blend and I can gaurantee you will fail.