Launch Window for inclined orbit

[VaPaL]

How do I calculate a launch window for an inclined orbit? Let's say I have to launch for a specific polar orbit, from my experience, if I launch at 92 or 95° (a little 'backwards to cancel the body rotation boost) when I'm just below the orbital plane, I get a final orbit that is anywhere from 2 to 10° of inclination with said orbit (depending on the vehicle performance). I have to launch a little earlier to get a closer orbit, but how much earlier? Normally I just eyeball it a little earlier and correct the inclination after. But that's not optimal nor good.

Any help is appreciated!

(Mods: I posted it here and not on the Gameplay Questions and Tutorails thread because it relates as well to science and space flight, but please, move if it fits better there! )