I can issue movement commands to multiple Xenonauts that have them end up in the same square, and they will then proceed to stack up there. So far, I've gotten 2 Xenonauts to stack, I have not attempted a third. I will test further and add screenshots.
Initiated starting mission.
Moved units simultaneously off the skyranger into the same square.
Soldiers can freely unstack unpeded.
Soldiers in the same square each block LOS appropriately, and it stacks. (I.E. If I have two Xenonauts standing, with each blocking 25% of the LOS, I can have a third shoot past them with a 50% chance to hit the intended target, and a 25% chance to hit either.) Burst projectiles calculate independently and can hit either Xenonaut.
Xenonautsv3-Soldierstack.bmp