ROM suggestion? STRICTLY for battery life...

[NewYorkLaw]

I am running the NYC marathon on Nov. 1. and wish to take my phone along, running SportyPal (gps tracking). I have been using it (happily) for a couple months now, but am concerned about battery life. I have a pretty new (OEM) battery, and under NRG's rom, with the phone off (airplane mode) and nothing running except for sportypal, I seem to get about 4 hours total life. I need to be able to make it 5 1/2 hours (hopefully, worst case).

So, which rom do you guys suggest as the one that will give me the best battery life with the radio and internet turned off? Literally, running nothing but sportypal, which uses gps. I don't care what other issues the rom has, or whether you find it particularly stable - it just needs to give me 5 1/2 hours of battery life with sportypal running.

Pete