Just some ideas: aliens have different 'visions' for exampe normal, infrared(sibils) and pheromone(xenos). Xenos had 10 normal 20 ired and 40 pheromone vision conbined.
Stealth-A armor cuts 70% alien normal vision 50% of ired vision and 20% of pheromonic. So Xenos can detect this armor with normal at 3 range/10 ired/32 pheromonic - so it will be 32 as highest. With tactical point of view stealth-a armor not best choise for xenos missions, but it may be much greater for adrons.
:random thoughts: