Going to solid engine and transmission mounts in your race car is the best choice for chassis rigidity as well as keeping the mass of the engine in place under the large G loads found on a race track.
But when you go to solid mounts there are other parts on your car that see more stress like the front cross member and the transmission cross member.  For the front cross member we build a weld in reinforcement kit that will keep it from cracking and for the transmission we sell an upgraded cross member that will not crack under the stress.
If you upgrade all of this at once you will be much happier with your solid mounts.