Serpent 960 going E powered. Need advice.

Hey guys, I am super excited about his. Monday I am picking up a Serpent 960 with a few 966 upgrades. Car is in pretty good condition and comes with a few hundred dollars worth of spares. Two sets of belts, four sets of wheels (two brand new), tow bodies (one new), two full bearing sets, extra set of new shocks, spring set, a spare 2 speed assembly (doubt I will be using it), and a fair bit more stuff that I forgot.

Anyway I am going to fit Tekin RX8/T8 2250kv combo in it (might even try the T8 2650kv too) . That is the easy part. I have pretty much figured all of that out but the part that is giving me the most trouble is the batts. Location and size. If I wanted to get roughly 80mph out of this car on 6S what would be the minimal battery capacity vs C rating that I should use. Not sure if I will be able to get away with big capacity batts if I try to mount them inside the chassis like I have seen done on the net. If I fit battery boxes to the sides of the car then I could probably run some decent packs but how will this effect the performance? If you look at the car in its nitro configuration everything has been packed into a narrow space along the chassis. If I go sticking two heavy lipos to the sides of the car I am worried that it will destroy the handling. Not going to race but I do appreciate a good handling car.

So any tips and recommendations I would very much appreciate the input guys. I would like this to be a decent and reliable car.