Piston to cylinder clearance?

Loose may not be what you want.
The clearance is there to compensate for piston growth as the piston comes up to the operating temperature to which it will be subjected to. For performance you want them as tight as possible without scuffing the skirts under the duress of racing. The fully expanded piston will keep the rings square and perpendicular to the cylinder walls.If you cannot figure out whose pistons you have or the type of material they are made of, then you cannot choose a clearance with any guarantee of success, unless success means loose and possibly slow.
Again Hypers are so stable that a clearance of .0015 to .0045 covers most applications.
Perhaps your buddy knows more than I was able to ascertain from your first post. If those pistons are forged, and you are going supercharged or Nos, then .001 to .002 will be too tight.