Power plants

I have been fiddling with the new Mabuchi motors that I received and so far they look large and promising.  At 7.4v they appear to have similar torque to my geared down Maxons but also appear to be even slower and more precise.  I am disappointed to see that they only have 2 M3 mounting holes as opposed to what seems to be a standard 4 holes.  I am looking forward to making a temporary motor mount and exploring how they perform.   Last night I confirmed that everything running off the main batteries can handle a maximum of 18v. I think at this point it is a question of what voltage I need to run them at and whether or not to equip them with gear boxes.

I have been looking into batteries and such and while I would like to use LiFePo4 (A123 chemistry) I can't seem to find the wiring needed to add balancing taps.  BatterySpace has a pack that looks promising but for no apparent reason, it is limited to 2A discharge and has the cells arranged in a very strange manner.  Right now, I am leaning towards using some of my LiPo batteries for testing if needed.