Recently I bought a Taiyo r/c f-16, which is similar to this below:

http://www.rakuten.co.jp/ggimport/658403/667691/681698/

The plane comes with a small 6V 3-cell NiMh battery and a field charge. After some simple assembly and testing, I realise that the plane motor works well, but the battery sucks - could not sustain the motor at full power for more than 40 sec. []

I'm thinking of replacing the stock battery with another 6V battery with higher capacity e.g. using li-po to improve the flight time, but I'm not sure how to go about it. What are the things that I need to look out for? [&:]

Appreciate if any one of you can help or direct me to some place where I can find the info that I need.