Need the best lipo....what brand?

[speed demon]

I'm running a rustler and going for speed. I have hit 84.9mph by gps with a medusa 2200kv and a dymond 6S 4000mah and a modded MM.

I used my eagle tree and during my runs I pull 74-76 amps for about 3-4 seconds. My lipo drops volts to around 3.4vish per cell.

Looking to hit around 88-89mph. Was hoping a lighter(smaller) lipo with less voltage drop to get there. What do you guys suggest? Thanks