Bubble trouble: What do I do when I'm the 3rd stack?

[Blindcurve]

I play the 11s. I like my game until I get to the bubble. (Or at least my flaws are manageable) Every second game or so, however, I get to the bubble and there are two large stacks, a short stack and me maybe 100-150 over the short stack. The big stack is playing optimally and keeping the short stack alive while pounding on me, and the second stack isn't defending himself. The short stack is trying to survive and is doing so because he's getting help.

What kinds of situations am I looking to exploit in this scenario? Obviously it would be nice to double up against the one of the bigger stacks but how much risk should I take to try to do it? Should I be trying to wait out the short stack? Play only premiums? Obviously the blinds matter...for the purposes of this discussion lets say:

Blinds 50/100 6 hands left.

Stack 1: 4200
Stack 2: 600
Stack 3: Me 900
Stack 4: 2300

If I could get some help or a line on a good thread on bubble play, esp. against a big stack who's keeping the short stack alive, that would be great.

FOITNOF,

-D.