What a bunch of lawyers!
Or perhaps test pilots, as presumably you all fly your aircraft to within the one mph, one lb, 10 rpm, etc that many POH have determined.
If so you're far better pilots than I will ever be. I'm, more a 5 mph, 20 lb, 50 rpm sort of chap. And that variation simply means that even the best POH is a guide. What really needs to be understood is that you (and especially I) will never achieve the figures in the POH (especially if it is an American type).
As such maybe POH are actually not that valuable. My Emeraude had two photocopied pages in French, which even I could figure out (speeds, weights, distances). My Terrier has 30 odd pages but nothing on fuel consumption and the 'handling notes' are meaningless.
Thankfully these machines are incredibly tolerant and v ery simple - they have fewer variables than the GPS's they are fitted with so they really don't mind.
p.s. Even if you plan everything to the last decimal point how precise is your wind estimation?