Does/will your Gentle Lady even have a motor? The ones I've seen are not powered, just gliders.

If there's no motor, then a simple 600 mAH, 4.8 volt receiver pack is all you'll need. That will give you at least 45 minutes of flight time before recharging, as long as you don't have any binding in the linkages. (Just be sure to charge your packs overnight before you go out to fly, or your GL will end up like the Aspire.)

That 7.2 volt pack was probably just a standard 6 cell pack. (6 cells X 1.2 volts = 7.2)

If you'll have an electric motor in the GL, then yes you'll need a Speed Control and a larger pack is recommended. I'd suggest a NiMH pack rather than NiCD's, in the 1500 to 3000 range. But the larger the pack the heavier it gets, and the harder it will be to keep the plane in the air.

Good luck,
Dennis-