I think the .61 would be too heavy too. The plane is supposed to be as light as possible for better aerobatic performance. I believe you should look for something like a Webra Speed .50 or Irvine .53 if you want more power than a good .46 will deliver.

I have a TT Pro .46 with a Tower muffler in mine. It's strong enough to hover and slightly pull out with a Zinger 11 x 5. I imagine I would get much better results with a 3.5 or 4 pitch prop, but there aren't any around this area. I ordered an APC 11 x 4 this winter to try out, but haven't used it yet.

I have no experience with the 4 strokes, but most of what I've read says the Saito's have more power per ounce than OS and Magnums.

Tim