I fly both O.S and Magnum four strokes. The 52 four stroke is equivlant in overall power to a 40 size two stroke. THe four stroke can swing a bigger prop and has better throttle response. Two things that are a pluss for a plane like the Pluse. You are not going to fly it at full throttle for more than a couple seconds at a time. What you want is quick and reilable throttle response throughtout the range and lost of low end thrust. I'm just getting my feet wet in a Phenoex Fun Star. I've got a O.S 52 in it cranking a 13x4 apc. I am flying at 1/3 throttle. In fact the meager instructions warn you not to fly at full throttle for any length as the control surfaces will start to flutter. I can't imagine a 70 on this plane, although the extra weight would be good. I had to add 6 oz of weight to the firewall and a 70 weighs just about 60z more than the 52.

I have a Magnum 70 in a Ruperts Dad, a build from plans plane that callls for a 52 four stroke. That one also needed weight up front so that is one reason I used the 70. The wingspan on it is about 8" longer thant the fun Star and the plane weights about a pound more. The seventy is a good choice for it. I crank a 14x4w APC withi it. Compairing the Fun Star to the Ruperts, the Fun Star seems to have a ton more power.

I also fly a Magnum 91 in a 4*60. Again all the power you could ask for. All three planes are not speedy, so the four strokes are great fits for them.

Don