If you have the motor laying around, by all means use it. I fly my magic with a used TT 36 heli motor using the stock heli pipe, and it hovers at under half throttle. My plane came in at 3 3/4 lbs and the mods I made are in the following threads.

http://www.rcuniverse.com/showthread...440&forumid=21


http://www.rcuniverse.com/showthread...451&forumid=21

The LA's are longer stroke engines, not made for all out hp, but they do have some lower end torque. And they are lighter. The key to these planes is to keep it as light as possible. I can see if you used all mini-servos, and a small 350 pack and feathter 6 channel receiver, you could get the weight to 3.5 lbs. Mine has all standard servos(mini on the throttle), a futaba 127 receiver, and a 1600 ni mh pack. Obviously, if you went to the smaller pack, you would need to recharge at the field after every couple of flights..