You're right on the money for the skirt, except there is no reason for all these piston manufacturers to run skirts shorter than stock, which most of them seem to do. Law of physics dictate that the skirt load with a shorter piston is GREATLY increased, as there is less leverage preventing the piston from turning in the cylinder, and thus more chance of a bent skirt at high hp or detonation. Mahle is a pretty light piston, and the heavy Atomic 'Fat Rod' combined with a light Mahle piston makes a combination which weighs exactly the same as the stock combination, only it revs much better as this piston is lighter and has less friction than the stock setup. Another problem is that tolerances given for the pistons are for race engines, which run 100% load for much of the time, and thus has much more thermal expansion margin built into the piston clearances. I have done a temperature test on the Mahle Piston vs a stock unit, and couldn't see much difference on the micrometer, so clearances for street use can be taken down somewhat compared to recommendations, just how much depends on the size of your balls, as too tight will result in so called 'black death' where the piston 'nips' the cylinder during load, and a hone and new pistons is the result. Hope this is helpful