Right. I did not build a square box extended from the wing bulkhead. As far as how far back from the spinner the new firewall needs to be, you will need to come up with that distance based on the length of the G62 plus cup mount, 5 1/2 inches sounds a little short. I can't say what that dimension is without removing my cowl. I'm not sure what you mean by glued to the cowling? You shouldn't need to glass the new firewall to the cowling just glass it to the fuselage proper. The cowl still needs to be removal for access.