Pros: KC highly recommends fitting both of these lower engine steadies to reduce engine movement and reduce risk of header cracking.
Cons: The RH side steady interferes with the factory fitted lower steady because they want to share one fixing point, but the thickness of the bracket makes that not possible.
Other Thoughts: When fitting to a late model mini that has the factory fitted, lower RH steady that reaches forward to the front of the subframe (and shares one bolt with this new one), you can use both parts together if you use longer bolts* and stack washers underneath the other two mounting points of the new part so that the new part sits nicely on top of the existing steady.
*I heard that intake manifold studs are the right thread/length for this but have not confirmed it yet.