Why don't you undervolt the frequencies independently? I can undervolt 300Mhz frequency down to 650mV rockstable. This is by far the most important frequency to undervolt, because the phone (should) stay the most time at this frequency.

Which powertop version did you use? With 2.7 i get errors about missing functions in the kernel and i*m not in the mood to compile a new one right now...

The blu_active governor needs alot of tweaking to be more battery-friendly than conservative. In its default configuration it goes way to fast to the highest frequency and stays there too long. So, a few tweaks are needed...