When removing material from the crown of the piston, take care not to hit the skirt or the pin journal. Make sure to deburr and clean before you take your next measurement.
We first start by measuring the base weight of each component and logging them down. Our goal is to get our mean weight within 0.5 grams. Remember, these are precision parts, use precision tools to do your measuring. We don't recommend a mail scale. Try to find a digital scale that will measure to, at the least, 1/10th of a gram. Starting with the pistons, we determined the lightest piston of our group and used that as the target. To take weight off, we choose the thickest areas that would least affect structural integrity. This is usually in the crown on the bottom side of the piston. NPD's box piston design limits how much can be taken out directly from the bottom of the piston, so care is taken when cutting away material.