I have a 77 Super Tigre 46 R/C, single ring, with muffler lugs. I made a .280 venturi, and am using a Super Tigre spay bar and needle. Otherwise, the engine is stock, with good compression. I have been running it on the test stand, and it seems real strong, however, when it breaks to a 2 stroke, it seems to take a little long to come back to a 4 stroke. This is with going from level in a good 4, to raising the test stand to almost vertical, and back to level. Is this a characteristic of this engine, or does it need tweeked, raise head? smaller intake? I am running 10% nitro, 23% 50-50 oil. It is going to end up on a fairly light smaller plane, so does not really need  to be a real powerhouse, just a good stunt run. I have been running it with a tongue muffler with the holes drilled out, and an APC 11-5 prop.