These inserts were designed to decrease the lateral deflection of the tire while at the same time increasing vertical impact absorption, to provide better handling in the bumps. Using a soft foam or hollowing out the inner circumference leaves the car feeling squirmy with a less accurate feeling through the bumps, not to mention a loss of durability. Gil Losi and Mark Pavidis knew this compromise was not the solution. The solution they found was the addition of lateral grooves to the inner diameter. The lateral grooves allow the insert to flex vertically, absorbing large impacts while still maintaining the lateral stability and overall durability AKA inserts are known for, providing you with a no compromise, high performance foam insert. The result is a more predictable handling car, with no sacrifice in insert durability.
I had made it softer to my liking through applying v cut technique at the inner rib of the tire as mentioned by Ryan Harris which gave a overall flatter profile that improves grip. I have also cut 1-2mm of the edges of the insert to soften the sidewall of the tire for improved grip. Overall, it is an insert that will last me many rounds of tires without much degradation.
So I need to spend money for this AGAIN.