I think the 7-4's are probably close to the best prop for those .09's, but the engines are just at the lower limit for the airframe. The total hp is what it is.
So far the Magnum .15 XLS I got recently is turning out to be a good sport engine, it powers the 2lb Mini Contender really well (longggg vertical and it will hover though I am a spaz at it) and seems okay on fuel consumption too. In fact I use a Hayes 3oz on this airplane and the capacity doesn't bother me because it's fun at 1/2 throttle and full bore. Mix it up and flight time is fine.