Your on the right track. I have that same plane. I power mine with a 1400 mAh Duralite Li-ion w/ regulator. If I had to do it over again I would just stick a 2000+ mAh Ni-MH in there. It may be a little heavier than the LI-IONs but you got to think about the weight of the regulator (1+ oz.). In the .40 sized stuff I would go with a 6 volt NI-MH b/c the weight will be the same at a lower cost.