I posted this question but got no answer. First time that has happened.

I have a H9 120 and want to put a G26 on it. The engine comes mounted on a aluminum plate with three flat head screws and 120 degrees. Why can't I remove the plate and mount the engine directly to the firewall? All I need to do is make the hole in the firewall big enough so the flywheel nut will clear. Has anyone ever done something like that?