so, we have the eagle 580 flying using an evolution 10GX motor... which is a 10cc gasser
the engine runs great, no issues starting or running it ever
the plane is an awesome plane to fly. It won't 3D with that motor but it makes a great tumbling plane which is what the cap excels at.
I wouldn't do it again... in this size plane, the weight of the motor + accessories is more critical than the power output of the motor. The gas motors are heavier than their nitro counterparts, and put out less power. Yes you get longer flights and save $$... but a .60 sized nitro isn't exactly a thirsty engine and you'd be happier with the performance and overall weight.
For me it is a lesson learned. I had decided that when I got back into the hobby I was going all Gas... no nitro or electric... the big gassers have been great for me, the smaller ones seem to work well in terms of running and reliability, but the weight is tough on the smaller planes