First of wouldnt 11.1 V be too much for your gun to handle? Secondly these batteries are pretty expensive, probably twice the price of the others, but they do last forever. Lastly Yea they are smaller but are you REALLY going to notice the weight difference? There like half the size of a normal batt but still. Also you should look into rc sites such as a sight called tower hobbies
http://www2.towerhobbies.com/cgi-bin...=++&search3=Go , they'd sell em forsure. One last thing im not sure if they would have the same fittings as the normal batteries. The ones i saw on the above^ site were for recievers in rc cars, to power the controller and servo's, not the motor.