If you are going to use those 3cell packs I'd reccomend a 13x6.5(that came straight from the website). On that motor that'll give you the most power. If you do go 4cell than just use a 12x6 and the performance will be great. I decided that instead of buying a new charger compatible with 4cell I'm going to put two 2450mah 30c 2cell lipos in series because I just want that extra power for $5 more per battery. Along with that I'm getting a 700watt motor that'll give me 2700grams of thrust. I did this because HobbyKing had mine in backorder and I just couldn't wait and this was the only other motor that seems to have enough power(infact it has more). Besides, torque 2814 for $80 or this turnigy motor for $25. Along with a 60A turnigy speed controller.