I had two issues. First one was some dead sticks or stumbling on the maiden flights after rolling, loops, knife-edges, and long quick down runs .
The cause was the supplied plastic fuel clunk and neoprene line in the tank on the carb line. The line was too stiff and the filter clunk too light and didn't allow it to sink and move back&forth I changed that out to a brass sintered clunk and Tygon line and problem solved.
The other issue was keeping the tune once tuned. I would get good runs but lag out on climbs or it would start 4-stroking, or run lean on dives. Retune the HS needle and it would be corrected for awhile but then go back to the issue. I applied some shrink tubing around the gap where the needle meets the body and problem solved(similar to the ol' glow needle fix). Either the needle was moving slightly(side-side) and/or a small air leak. After that it held the tune and ran great.