kulivontot - Nobody around here rides 2 different bikes with crank lengths that vary by "1cm?" If the OP is riding 165mm cranks on 1 bike and 175mm cranks on the other, I'd say he's got bigger problems than worrying about fore/aft saddle positioning. I could see maybe a 2.5mm difference between track and road bikes; that's how I always spec my road and track bikes, but 1cm between 2 road bikes? C'mon. Also, most of us know to ride the same model saddle from bike to bike.
Clearly you must not own enough bikes if every bike you own has the exact same crank length and exact same saddle on every bike. I own a variety of different road bikes, some of which have vintage non-ideal cranksets. I'm not about to go scouring ebay for period-correct cranks of the "correct" length, when I can just account for it with the fit. Op is asking us to solve a trigonometric equation of a difference of half a degree; the difference is going to be measured in millimeters, which contrary to what you may believe are indeed noticeable. If you do your bike fit by feel, then by all means ignore small deviations, but if you're going to take the time to make measurements and try to dial things in exactly, you might as well do it right and account for the little things.