Chris,
If you play just fo ICM, you’ll be down to about two orbits’ (8 hands) worth of chips when the small blind blinds out, even without an ante. That puts you in a mighty tough spot. If you shove with the 8’s and everyone behind you folds, the small blind is getting huge odds to call (call 25 into a pot of 40). Expect to get called very widely and be facing at least one overcard. No way the SB can let you pick up the blinds here at his expense. Your shove becomes (at best) 25 to earn the 15 already in plus the SB’s 25.
All that said, if you shove, the players behind you will recognize that the SB has to call and likely fold themselves unless they have a huge pair. So you’re unlikely to have to go against more than just the small blind.
The charts say shove, and I believe them. There is a large possibility that no one behind you or the BB has anything with which to give the SB a hard time, and this will be one of your few remaining opportunities with a decent hand to gather in chips. Time to shove and take advantage of everyone else’s hesitance on the bubble.