BlainSmipy, I too would love to follow your project, as I have contemplaited building a 577 Light Nitro on a very strong 12 bore frame. As of yet, I have not found the frame I will use.
My guess is the AYA 10 ga. will be plenty strong for your project as these were ment to handle heavy loads for serious use.
Good luck, and please keep us informed as to your progress.
Norman