Nano Techs are excellent but as said not BRCA legal so I would not bother as some clubs and events you wont be able to use them. I got some 4800mah Gens Ace saddles from giant shark rc. They are only £25 and really good no probs and BRCA legal. Only 25c rating but still feel punchy to me in my 2wd, dont know about 4wd if you would need a higher c rating?
http://www.giantshark.co.uk/product/...ck-saddle-pack