I just sent the money out for a om 540p.i cant wait.im currently flying a sig se with a 46fx and a macs muffler.the plane weighs 5lbs and it will climb from a hover no problem.i cant imagine what it will do on a 4lb 540.i guess what ever motor you get will pull like crazy as long as it throttles good.good luck.
p.s. try magnums there strong and run smooth.