Yodog, please keep it simple. Just having the dual rack steering with the shorty lipo will help the car enough. If there is enough room left over to allow the option of mounting the battery more forward or rearward, even better.
I am more concerned on how you plan on retaining the battery onto the chassis. I hate using tape and I've seen too many instances where the battery pops out of the tape after a hit. Perhaps you should take a look at the Exoteck TA06 chassis regarding battery access without the use of a removable top plate.