I made my boys 2 cell set-up with the battery north to south. If you add a few spacers to the rear mount, you keep the same shock angle. It's still 200mm, as that is what we are racing own here. Whole thing cost nothing as it was stuff I had in my toolbox.
Had a race last weekend and it really was on rails. Quite amazing considering I know 3/5 of stuff all about pan. Lucky build.
I used a rear tweak spring mount from a CRC car and shaped it to fit for the front end of the centre shock, and used some stand-off tubes with 2 new holes in the chassis. Then I made some CF side strips to stop the battery moving sideways. I just put a single strip of tape at the front to stop it moving forward (haven't mad a front-stop yet.
These cars handle 2 cell Lipo very well considering they are just big versions on the 12th cars.