The 61 powered airplane ran about 150 mph. Not quite fast enough to run gold. I did end up clocking a 1:27 with it on a practice flight. The Macchis are my own designs and quite a bit cleaner then the WM Mustangs though. I would think that your setup running an 11x9 in the 13K range will do well in silver. My silver airplane was powered with a Rossi 45 spinning an APC 9x7.5. Best time with that one was a 1:39. I broke out more times then not but it's all fun. You may want to spend some time looking through the scale racing threads here on RCU. Lots of good info there.