I've come up with an MX5 fabricated rear diff cover that allows it to be fitted where a sierra unit might usually be found. It still relays on the nose of the diff being supported but all so gives another 4 12mm holes to bolt/clamp too.
This is mk1 version of this cover if there is any interest I'll work out how it closer to the original shape.
So have I wasted 8 hours of machining ,cutting and welding or has this got a future?