Have you tried this GE ROM - http://forum.xda-developers.com/showthread.php?t=2356276
I've been using it for quite a while now and with Faux's kernel, I was able to achieve over 6 hours of screen time. I reflashed the ROM and have been using the stock kernel since last week. This is what I was able to achieve...
Image
That was at about 75% brightness and on Unicom 3G for about 5 hours.
I haven't tried that one but will do so ... Thanks