@Walks
Well this is how i see it, for future reference with similar situations.
I use success tests in situations where I feel the actual character doesn't have a great deal of control over the opposing npc's test. I just basically feel that in a realistic scenario, when you dive through someone's legs, you need a certain amount of momentum and really your acrobatics test is taking total precedence because you goal is to get through....and once you're flying through the air, that's it, you're committed to the maneuver and there's not a whole lot you can do to make it all that much quieter. The only factor I felt could really have a noticable influence is you're traceless walk, so I included that. If you had been wearing steel toed boots or been an ork then the threshold would have been 1 for the trolls perception test...I would have even made the threshold 1 if you were defaulting on the acrobatics test because you obviously made it through the legs through shear luck but you don't know how to land smoothly at all....you'd come tumbling down.
I get threshold numbers by imagining how hard it would be if i just described the scenario in a generic way (i.e. an stealthy elf-chick just dived through the legs of a troll and landed behind him=threshold 2 to notice it IMO).... then all the finer specifics come into play through modifiers to the dice-pool. The specifics of our situation i.e. he's distracted, he knows that when you hear something like that it probably means something (that's why he thought it was a devil rat...because it's happened to him before), you have a magically silent contact with the ground....all come into play through their modifiers to the dicepool.
Then when you're just standing their behind him, I feel that if infiltration affected affected being seen by the troll, then I feel the SR developers would have made chameleon suit give you a bonus on your infiltration roll, but it always applies instead to the perception of the observer because you could just be standing there and someone would overlook you. Same thing with traceless walk, it seems that if all contact with the ground was influenced by infiltration, then it should give you a bonus to infiltration, but instead it affects the observers perception because I feel SR developers didn't intend infiltration to basically be the skill of controlling how much sound each one of your individual movements makes.
Of course there's arguments for doing it differently, but this is the way I see things.
