Crippling Strike Questions

[The Viscount]

Crippling Strike is a neat little ability gained by Rogue, Justiciar, Bloodhound, and Thayan Slaver. Rogue, Justiciar, and Thayan Slaver's Crippling Strike work essentially the same way. When they sneak attack an opponent, the opponent is dealt 1 or 2 points of strength damage. Bloodhound simply states that it deals the Strength damage against its mark, but refers you to the rogue ability.
I have two questions.
1. Does a bloodhound need to render its mark flatfooted or flanked to use crippling strike, and if so does the bloodhound need sneak attack?
2. If a character were to have more than one form of crippling strike, do they stack?

[Venger]

1) there's no sneak attack given by bloodhound, nor is it required to enter, so it seems unlikely that it would be required to trigger crippling strike

2) if you were able to qualify for more than one of these things at a time (and congratulations if you do) I think the standard rule of things coming from different sources stacking would come into place.

I could be wrong though. I'm not sure about this. :/