E58 400 plus HP Dart sport build

If your engine builder has problems with KB hyper pistons breaking, you need a different engine builder.

This...

They don't have a clue regarding machining tolerance and/or most important ring gaps. They are likely gapping rings using the .004/inch of bore. If you do that with a hyper, it will break the tops off from rings butting. I've had hypers running a 200 shot and never had a issue.

If they are just pulling rings out of the box and installing them, RUN. TELL them that you want the top ring gapped at .0065/inch. so if you have a .030 360 with a 4.030 bore it's going to gap at .026 and if running a small nitrous unit .030

Bad tune ups kill pistons as well. Detonation is the enemy of all pistons.