Converting Kyosho ST-R, new to brushless conversions...

[pumpkinfish]

Ok I am currently pricing some options and I have a question about the cells. I have decided on the 4S2P 8000mAh packs but need to know realistically how many cells should I show up with on race day ready to go? I was thinking two. If I had to recharge a pack at the track, it would be no problem, but I prefer less hassle if you know what I mean. Too many other things going on to distract me...lol!