we need more info here cause something not adding up....
they want to put a delipped piston in but dont want prior older pistons because it will throw off balance
somehow the balance was done with no pistons or at min, 7 pistons
they are telling you only 11-16 pistons will work on those rods.
they cant balance the rotating assembly with out ALL the pistons on hand. if they are leaving the rotating assembly alone, all 01-16 pistons will work on your rods, you just have a narrower wrist pin head on the rod, it wont cause any ill effects over time (few guys i know have done this with many miles under their belts thus far).
if you are going to do a delipped piston, ditch the 06-16 pistons all together and put 01-05 pistons in and have them delipped. either way, the moment your stockers are delipped, you just threw off "the factory" balance (which there isnt much of) so might as well put a stronger piston in that isnt overly heavy ( i dont have mahle race cast weights to compare to a delipped lb7/lly to say its worth changing.
But in my honest opinion, you should have had the rotating assembly balanced to make that crank last as long as possible which means you need all the rotating parts (bearings, rods, pistons, rings, wrist pins, circlips, etc) to do so.
