A friend had one of the .61's, and I saw a couple others (also .61's ) fly at various pattern meets during the mid 70's...
They ran ok, but didn't impress me as being any better than the Webra, or Kraft, O.S. FSR's etc.

If you installed the super quiet insert in the muffler, it really choked it down. (you can see one of the inserts in a couple of the pictures ) The rear end cap of the muffler un-screws and you can run it 3 ways...either as an empty can, or with either of the 2 inserts.