It's all good I believe for instance that the reason for running a factory cast piston so tight as opposed to a forged one set up loose is mainly in the design parameters. One of which is material. Some good reads.

http://blog.jepistons.com/understanding-piston-skirt-design

http://www.enginebuildermag.com/
from this article
"Some people think that the same thermal characteristics that allow forged pistons to run cooler also causes them to swell more as they heat up. Consequently, there’s a common misconception that forged pistons always require greater skirt-to-wall clearances. This is a notion that isn’t necessarily true because clearances depend on the type of alloy that’s used in a forged piston, the design of the piston itself and the application in which the piston will be used. [/b]Some forged alloys actually have a lower coefficient of thermal expansion than the alloys commonly used in conventional cast pistons!"[b][/b]

If a forged alloy expands less why would we run it looser. For performance reasons, which requires a skirt redesign.