A reason 4 strokes are better for 3-D

Basically fellas 3D flying (pulling out of hovering) comes down to static thrust. This is the thrust that your engine produces when the plane is not moving. Oddly enough the pitch of the propeller only comes into play indirectly. The major factor is prop diameter and RPM.

The prop diameter is so important because static thrust increases cubically (not squared) to the diameter of the prop that means that if you swing a 15 inch prop with a four stroke and compare it to swinging a 13 inch prop with a 2 stroke, at the same RPM, you are gaining 50% more static thrust. Now you can make up for the difference with the 2 stroke if you spin the prop 50% faster than the two stroke. But that means that you need to spin the 13 inch prop at about 15,000 rpm. The problem with the two stroke is that because it produces less torque it will take it longer to reach 15,000 rpm. Than it would for the 4-stroke to reach 10,000 with their respective props. This means that even if you could get 15,000 rpm from the two stroke, unlikely, the throttle response ( which is very important during hover) would be slower than the 4-stroke. This is why 3-D fliers have gravitated toward 4-strokes.

The way pitch comes into the equation is that when you increase the pitch of the prop (increasing top speed), or the diameter (increasing static thrust) you increase the horsepower you need to swing the prop. This is why 3-D fliers use lower pitch props. Usually in the neighborhood of about 4. This allows them to swing a larger prop (thereby increasing the static thrust), while sacrificing top speed (which is not that important to a 3-D flier anyway).

All of this logic applies in reverse for High speed aircraft.

I hope this has answered some of your questions as to why 4-Stroke engines are more suited to 3-D flying.

Oh and one more thing. I would put my UCD with a lowly 70 surpass against your 2-stroke any day. And I would win. Not just because I have physics on my side but because mine is better.

Nmking09