A small brace is going to be made to stop the nose of the diff going up and down which will be integral with the rear subframe.
The gear box mount will go where the first of the tunnel braces go.
There won’t be too much stress here because the unlike the RX-8 FD engine mounts are at the rear of the engine and its on polyurethane bushes already. To give you an idea, when I take the gear box out, the engine stays in the same position. I’ll post some pictures when its done.