ORIGINAL: pizza
Ok dickymint, you will learn the hard way just like me and many others. there is a big difference between "power to weight (punchout power) and weight releative to air molecules. I prefer to supercharge a small engine and save lots of overall weight which makes 3d stuff much easier and safer close to the ground. you don't like your foamy because it has good punchout power but because it flys in slow motion - floats down like a feather or potato chip is very forgiving when mistakes are made - if you want this same feel you have to keep it light
I dont see how you can say that 4-strokes wont work for 3D. I have a Saito 100 in my Funtana, and it is just about one of the best fun fly planes it size that i have ever owned. I have a video of it racing a UCD in vertical. It flies straight up just as fast as it does in level flight. The "punch power" (if thats what you want to call it) is enourmous. I have found that 4-strokes are better on light 3d planes than 2-strokes, because they can swing a large prop. You really dont need a lot of RPM, just thrust. Running a 15x4 APC on the Funtana provides much more thrust than (lets say) a YS 45 with a 12x4. Even though the YS will swing the 12x4 at around 12000, I can get more power out of a 15x4 at 6900.
If weight is what you are looking at, then the 4-strokes still dont have a problem. My Funtana with the 100 is 6.5 lbs, not the lightest, but it still flies awesome. A UCD with the same engine weighs 7.5 lbs, still with plenty of power for all low to the ground 3D. The UCD at 7.5 lbs is a total kite.