⟨06Starscraper⟩ Well, I've been experimenting around to see if I could find the formula for getting the orbit normal vector in game coordinates from Principia's Inclination and and LAN values.
Using kOS "print vcrs(body:position, ship:velocity:orbit):normalized" to get the orbit normal vector. Or, anti-normal, as the case may be. I dunno of the left-handed coordinate system flips it or not with kOS's cross product - but whatever, the important thing is it's orthogonal to the orbital plane.
And I seem to have gotten the formula. But there seems to be a small correction factor "L0" for the formula, which is kinda odd.
x = -sin(LAN + L0) * sin(Inc)
y = cos(Inc)
z = cos(LAN + L0) * sin(Inc)
L0 = 5.37
This seems to get the correct vector components by about +/- 0.005