I had a similar problem with the .52 mid-range. Found an old .46 OS SF carb, bolted it on, and instant success. Also, the notorious Tower muffler bolts on the .52 and adds many 100's RPM's on the top end. I had the CG way back on the two I had, and they flew like they were on rails and landed like butterflies. The .52 is heavier than the .46, so the plane tends to be nose heavy with the .52. I put a square pack battery back by the servos, packed in tightly with foam and it balanced with no weight on the tail. My first one with the .46 and tower pipe balanced with no problem and a AAA pack by the tank. Neither of mine would knife edge very well, as the fuselage is not very tall on this plane, but it did everything else great! I am considering getting another one, as I hear they are now coming with monocote, instead of that horrible oracover stuff. On my second one, I used MG Hi-torque mini sevos for the rudder and elevator, with no problem. I used std hi-torques on the ailerons and a std mini on the throttle and AAA NIMH battery pack. When you take nearly 6 ounces of weight out of the equation on a plane this size, you reap great flying dividends.

If you are not sure of where your balance should be, the plane should fly inverted with only light forward stick pressure for straight and level flight. If you have to push forward on the stick too much you are most likely nose heavy. Once you get it properly balanced, it flies awesome! There are some great threads here and online on perfoming thrust line and lateral balance flight trim checks. This plane is definitely worth the effort to get these things right. It taught me allot before I started bigger and more expensive projects. You can also mix adverse tendencies out, with a good computer radio.

Happy landings!