SS piston dish

[Bob]

Originally Posted by Sean Cour

A dish could be 40 holes drilled in the piston. Unlike stock, the piston just need to be measured legally for some kind of dish.

Unless something has changed in the 2015 rulebook, 40 holes weren't and wouldn't be legal. The rule has always been (straight from the rulebook):
"Replacement pistons permitted, provided they do not increase
stock compression ratio and retain overall design pattern as
specified by automobile manufacturer. Dish pistons must retain
half of original depth, and original diameter and configuration."

That is to say, yes you need to keep the original dish design. And you need to keep at least half the original depth. The remaining CC lost by a shallower dish can be acquired by valve reliefs.