I like that you use those ferocious convex hull shapes for your test. it exposes weaknesses in the engine.
here is a suggestion for your own production test, the convex hull can take a tolerance parameter. I am not sure if you pass it as 0.0
passing 0.0 makes exact convex hulls, but they force the the engine to do lots of work for very little reward.
this is because exact convex hulls can have many points that can be so closed that they do not make any contribution to the collision system since they generate contacts that are so closed that they produce rows in the matrix that are linear combination of other rows. that's bad.
The engine has to run expensive eigen values decomposition algorithm to prune these contacts.
if the contacts are not there then those algorithm take not effect.
if you pass a larger than zero tolerance, something like 1.0e-3, you will see the result is such that you could not tell the differences. but it can be much faster.