Copied over from the old forum since I just posted it like two days ago.
I noticed a while ago that on some of my ground vehicles, placing a decal as two-sided caused an issue where the decal would be placed where you wanted on both sides, but it would also appear distorted or mirrored somewhere else on the vehicle. For example backwards on the back of a turret or stretched on the fender when it was originally applied to the hull. This doesn’t occur when placing a decal one-sided or mirrored, only when it is two-sided and flipped to be the right way round on both sides (option two when placing it.)
The best example I could find is on the Finnish T-34-85 in the Swedish tree. If you want to see this, try placing a number decal in two-sided mode somewhere on the back half of the turret side. While you’re doing so, look at the back of the turret. You’ll see it there as well, stretched and distorted along the back.