TOM, you make good points. If I might add Prop selection has a lot to do with the flight
of an airplane. As an example my GP little Toni has a OS 110 4 stroke in it with a 12x12 apc.
It scoots along at 115 mph with that prop but has no vertical to speak of, not much thrust
but good speed. If I put a 16x6 on it, I would have much more thrust and vertical but would be much
slower. As it is an F1 pylon racer from the 50's, my prop selection is valid. Is it a 3D plane, no,, so I
am not concerned about thrust but more so prop air speed. Prop air speed = rpm x pitch / 1056 (static)
I know you know this but the OP might get something from it.

Tim
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Seems like most Four Star 120s around this area flew with glo 120 2 or 4 stroke engines. Most seemed to be a pretty good match and flew quite well without excessive engine weight. I would think the the DLE 20 would fit right in there performance wise. The wing area is huge though so a 30 wouldn't be as far off base as many would suggest. More power doesn't always have to suggest 3D performance. Some of us just like a quick climb up to unlimited inverted flat spins, etc.

PE,
So I would be better off with a Zoar 16X8? Thanks for the help, this is an area I know very little about!
Steiny

Had a 4*120 w/ a 26cc w/ mag on it had plenty of power

Also remember that an oversized engine will put a greater structural load on the plane. The landing gear and frame around it will experience much greater loads with a heavier engine. Same applies for the firewall. You could beef up the structure to take the heavier stresses, but then you would add weight and negate some or all the power gained by oversizing the engine. Also remember that gassers induce greater vibration stresses on the airframe than glow engines (or especially electrics) do.

The wing loading is going to be alot differnt with the DLE 20 vs the 30. Chances are your not going to use all that power but you will increase your stall speed and lose some of your areobatic performance because of the increased wing loading. stalls will also be more violent

I gent at our club has a 4* 120 with an electric setup and it has so much lift he clipped off the last panel on each side of the wing. It is close to the same size and wing shape as the Ultra Stick I fly with the DLE-20 and the vertical performance and top speed are like night and day between the two. I am not sure of the weight on his 4* but it flies much heavier than the 8 pound UStick/DLE-20 setup. He has a 16-8 prop and the DLE-20 on mine is using a 17-6. I did a static test with mine using a digital fish scale and got 15.2 pounds of thrust even with the losses like the wheel friction etc. I am certain the DLE-20 will pull it very nicely on the wing or not.