I have this battery. It does not fit inside the stock unless you hammer out some little tabs in it. It's pretty tough but once you get them out you're golden. I highly suggest you get female deans connector on the battery and solder a male one in place of the mini tamiya on your gun, that's what I did. If not, get the standard gauge wire and mini tamiya connector.
Edit: You must get the 8.4 volt (7 cell). The 9.6 volt will not fit no matter what.