One way film doesn't really exist. You might be better off with it inside or outside due to diffraction before/after the partially reflective surface but it's probably not huge. I would guess you're better off with it on the outside if anything as you're more likely to get reflectance (the beam is closer to normal angle inside the glass so you get higher transmission). But my optics knowledge is rusty as shit.
Yeah they probably know better than me which side is optimal, but either way you should get 95% of the performance on either side of the window (until it peels off I suppose)
Soul
frankenbike
One way film doesn't really exist. You might be better off with it inside or outside due to diffraction before/after the partially reflective surface but it's probably not huge. I would guess you're better off with it on the outside if anything as you're more likely to get reflectance (the beam is closer to normal angle inside the glass so you get higher transmission). But my optics knowledge is rusty as shit.