Ok I have done a bit of digging....
LRP x12 5.5 has a nominal power (in or out I dont know, assume output for now) output of 486W so at 7.4V that means at the very least 65A (I would assume that to be continuous rating). Seesh, I will do some calcs on battery, wire and connectors resistance and see if there is anything to be had. Acutally, I think this would be only of interest to a stock racer where a higher voltage at the motor means more power output for the same current and therefore less heat......
Any imperical readings would be great if someone has done some dyno work.....