[Finnster]

I know your pain, I've tossing similar options in may head. :)

The problem w/ all the A123s (14cells) is its going to be insanely heavy, esp in the rear. I raced around w/ 10 A123s, and at the last little bash 9 (tho I barely gotto run it, seemed pretty decent.) 14 cells is over a kilo. Going to 1P won't give you enough amps or runtime.

If this is a dedicated racer I think it will be a bit disappointing.

The single batt is easiest, but I would say you can cut the Mah down to save some weight. How long of mains do you want to run? If its mostly vs elecs (like at the barn) you really only need 10 min. Seems like a lot of nitro mains are only 15, maybe 20. A 5000 mah pack would give you over 25 min realistically.

To make a lipo saddle pack would be tough. Most higher Mah packs are too long based on the measurements you sent me.