[PorkChop]

First up, glad to hear it sounds like you're OK Skov, that could really hurt if bits of metal get loose!

Second of all, the issue of mounting the MX-5 diff has been discussed, at extreme length, in the past when Nathan suffered a diff failure during testing. Now, the reason for his failure was different - it wasn't bolted in correctly. But the discussion that followed concerned the diff nose mounting specifically. Keith Tanner's build used a box section frame, with captive nuts, and a part of it was welded to the transmission tunnel. In other words, the nose was solidly mounted. After a couple of years, he removed it during a diff change IIRC and found no issues with it whatsoever.

Every kit car manufacturer that uses the MX-5 diff has solidly mounted it AFAIK, including the diff ears (or in the case of GBS, cut them off altogether and bolted the top part of the diff to the chassis).

Now, I'm not a trained engineer, but it appears you need to replicate the PPF. The PPF is solidly mounted to the diff and the gearbox tail. There are no compressible mountings between the two. This fits in with what the kit car manufacturers have done.

So do I think that a broken diff arm (Mazda deliberately engineered a failure mode in the arm) is an inevitability? No. On my newly acquired build, I have a set-up identical to Johno's design, where there are 2 rubber Land Rover V8 engine mounts, fitted so that 1 mount would always be in compression. I'm planning on substituting these mounts for 1 piece solid versions in a material such as ali or nylon. The diff ears will either be polyurethane or solid again.