On a standard diff casing?? probably a good idea over 350bhp??

on a Thickwall case like mine?? probably over 450bhp??

I am guessing though to be honest.

I always think preventation is better than cure....

Mike does a cheaper plate as well though and for the amount it costs, I would put one on anything over standard power really for piece of mind!

Even if you have a Thickwall case its well worth putting a plate in at least if you don't want to stretch to the full cover