1 comment on that - the bolts are in shear. eventually, it will snap them if there not tough enough.
As for solid mounts all round, you need to allow SOME movement due to chassis twist. No matter how braced it is, the chassis will twist in corners and over bumps. the mild steel diff cage will twist, but the cast diff wont. To be honest, I think a stiff mounted diff is more likely to fail than a bushed diff. Think how much damage a car would get with no suspension at all?
