A few more comments:

I have fitted the plane with a Thunder Tiger .46 pro and found, like other posts, that the standard muffler won't fit into the muffler cavity in the firewall - this will likely be the case with any OS-like engine you attempt to install. So I ordered and mounted the Slimline Pitts muffler (the one for OS.46FX) and it fits perfectly. I added a couple pieces of silicone extension to the ends to get the exhaust well clear of the cowl. With this set up, post flight cleanup is minimal. I also found that using a .46 engine with battery and receiver stowed (stacked) 1" back from fuel tank (I made two crossmembers out of popcicle sticks CA'd to the fuse rails and strapped the stack to them) the balance comes out nearly perfect.

I also think at .46 engine is a good choice. The balance comes out right, cowl cutting is minimized and I think there was plenty of power. Remember, this is meant to be a scale-like flyer, not a 3D hovering machine! Note that I live in AZ, and flew it in 102-105 degree weather at approx. 1500 ft. ASL with no problems. If you just had to have more power, you could maybe go to a .50-.52 size engine (meaning if you can find something close or identical to the same dimensions as the .46), but I think going to a .60 size engine will make the model too heavy and adversely affect is flight characteristics.

I do agree with many of the posts on this model -- an outstanding value for the price (I paid $135+tax at my LHS). It absolutely looks great. The details, the shape, the colors, the build quality are all great. It is a bit heavy, but I believe this comes from a very sturdy build (certainly the opposite end of the spectrum of my Funtana). Some of the hardware is on the interesting/inexpensive side, but all works just fine.