I've reviewed and used many gas engines in this size and I suggest two. #1 is the Zenoah G-26 with no electronic ignition. I run mine on 32:1 ratio and I'm swinging a 16x8 at around 8000rpm. With the magneto ignition they're a snap to install and setup, easy to run, and with their extra weight they usually take care of any balancing issues you may have. I have mine on my Giant Big Stick and it's a great performer with no headaches. #2 is the SPE 26 if you just must have electronic ignition. I run mine on the same prop and gas mixture as the Zenoah and they're goof proof. One nice extra about the SPE is that it has a choke but it's also about a pound lighter than the Zenoah. If you go with the SPE you'll probably end up adding nose weight for balancing. I had an SPE 26 on the nose of my CMPro AT-6 and my Flyboy Models BV141-B and they performed great. Both of these engines can usually be had on RCU for under $200 shipped.