What the actual formula is for mission success probability, and for detection of units on a mission? I know for example that using allot of units on an assassination/abduction mission if your enemy even one other unit is almost guaranteed to fail, but if they don't it gives a higher success probability. Anyone know the number of units after which your chances are decreased?

Have you tried using one or more characters/units as decoys? I don't know the exact formula, but the manual says something about using decoys to distract the local garrison and allowing the real agents to work unnoticed. I think it also mentions something about not sending too many units on a covert mission (crowd of armed weirdos draws too much attention). Sending two experienced characters as decoys and a bunch of commandos/less experienced chars might do the trick. At least it worked for me most of the time.

It actually works just as well to use characters not terribly suited for the mission as decoys- such as those characters who are just about average in all respects, or who were only good for R&D. I've noticed that a lot of the novels in Star Wars have some basis in Rebellion, and so tried out the Zahn approach of using Wedge as a decoy when he would be a terribly obvious backup agent- it works fine.

 

But no, I've no clue as to the exact formula, though I usually use three decoys for one worker, four for two, and almost always the store-bought brand.