They are fine afaik, the only problem found was heat (tested on a drag car)
caused the resin to opaque, this was rectified with a change in resin for chem/high temp.

The thickness is around 3mm pure carbon so more than up to the job, it would be an good test to try them on a rally car as this only really stops the strut from falling down the turret, but if the car is on jumps and stuff where the full travel of the suspension is frequently experienced then this would show any fatigue/strength issues

Ive not seen many designs out there, heard lots of stories about people using metal inserts and all sorts but never actually seen anything substantial.

Its always better to have a composite part made thoroughly from the same material, only difference I think are acceptable are fabric weights

Hope this helps