the Biplane AeroAce weighs just under 20 grams, the mono wing weighs 17 grams. a standard 9 volt battery weighs about 45 grams. thats just too much weight for such a small plane, you'd have to switch to dual N20 motors and up the battery size quite a bit to be able to get that high of a wingloading to fly, and if it did fly, it would be a rocket
you can solder LEDs in parallel with the motors to get some light going (a resister might be a good idea too, an LED probably wouldnt like 3+ volts). if you do it this way, you dont add any weight but the LEDs themselves - no seperate battery to power them.
if you have the bipe, try removing the bottom wings. it'll lighten the plane, make it turn sharper, handle more wind, but your speed will be up a little.
i've attatched some pictures of some of the planes i've made from X-Twin/AeroAce planes electronics - there's an endless amount of designs you can build with these things. if it has two engines, it should be able to fly. (i also added pictures to my gallery. feel free to browse and ask questions on any of them, they're all really fun planes.)
nick