there's quite a few folks here that have helped me with engine tuning advice and they are very knowledgeable (opjose, greybeard, edmooreman, etc.). I would make sure to ask at least one of them directly.

If your engine runs just fine for 4 minutes (idle, transition, high speed) then quits, it sounds like a fuel delivery problem or possibly is set too lean and overheating. It'll lean out in the air. Have you checked all the basics? Can you see smoke trail in the air? Make sure you test with your tank half full on the ground. Are you getting bubbles in the lines? Have you checked all connections and performed a pressure test? Check that clunk in the tank isn't twisted forward. Is the carb significantly higher than the centerline of the tank?