RE: Sportster 60 power
The SS is a nice little stunt plane and engine size depends on how you plan on flying it. The .61 for me is a bit under powered and the 75 may be a better choice. I had the OS .91fs in one and it was OK but a bit more power would have been better. These are old designed kits and the .60s were the norm back in the day, we have much better choices these days.