This is 25.5 and the shortest I'll go when I go there. My sweet spot is around 26.5" though I'll wear 27.5" (but it creates a casual look). The tradeoff for me is that shorter A-2s can often look more stylish, while I feel more comfortable/confident/natural with longer jackets than ideal, even though they may approach an untidy look visually. I've grown to prefer the loose and long "Harrison Ford" fit rather than the ideal short/slim fit. Idk why really.
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When I bought my custom A2, I sized it so the leather portion ended at my natural waist, right around the bellybutton/top of pelvis. That put the knits just over my belt with my Levis.
Maybe that's not correct, but it seems to look ok, at least according to you guys.
I'm 5'6", and the back length on mine ended up being 23", including the knits.
If I buy an A2 (I still can't decide), I'm thinking 26.5 inches. HD is my height and looks great in a 26 - I know everyone has different proportions, yadda, yadda... 26.5 is what Shaul at US Authentic recommends for me. I'm 6'2", 185 pounds. I have a Raider (the one with knits) from G&B which is 27.5 inches long and it looks pretty good but I don't mind going a little shorter.
I've had long and short and I just got a Good Wear Perry A-2 that is shorter than my usual fair. I like it as I don't sit on it while driving or going to a movie, etc.
Seems to me, a flying jacket would likely be more comfortable this way, but the pics are all over the place, so wear what you like!
Honestly, everyone here and elsewhere has an opinion, and what does it matter?