[wilf]

If you go onto the Keith Black (Silvolite) pistons site, there is a table somewhere giving piston ring gaps in terms of thou per inch of bore for various applications.

Forged pistons are: heavier, require larger skirt clearances (piston slap when cold), but are tougher, and will stand more abuse.

Hyper pistons are: lighter, run with lower clearances, so quieter and potentially better oil control, but will break easier with mistreatment. Cheaper too.

In a real world, you could use NOS occasionally with hypers, but you better have your mixture, spark retard, and ring gaps right first time, or bye bye piston (s).

Of course, now will follow umpty-three posts from people using NOS, blowers, turbos and 15:1 CRs that detonate like bast*rds , with hyper pistons, who never had a problem.................

My own engine (never designed to have any kind of power adders added afterwards), has hyper pistons, and I "exercise" it fully regularly, and have done for 18000 miles.

However, if I had built it with NOS in mind, I would have used forged pistons.