I own several of these engines. All run fantastic. However, as with any engine it will take a little tuning time to get them in the sweet spot. My favorite prop for these is the APC 11x4. Works great for 3d planes and works great for trainers. 10x6 is great for break in but I ran through a set of bearing with this prop. It spins extremely fast, makes a lot of noise, and not as much thrust as a 11 inch prop. 11x4 will get you off the ground fast, act as a brake for landing, and not overspeed the plane which is helpful in training. 11x5 is a second choice and will quiet the plane down a little further. I use thunderbolt 4stroke plugs which are about the equivelant of the os#8. They used to be called 2/4 stroke plugs but now they are renamed. You can get them from hobbypeople.com and the best part is that they are only $2.95 compared to the $6 os equivelant. They work great in all my engines all the way up to my 23cc Super Tiger. I've had them last several seasons with no problems. Always a single backflip to start the engines once tuned properly. USE A LEATHER GLOVE with this method for safety. An APC prop can chop your finger off without a hesitation.

As far as cold running I don't suggest it in your case. Bad for the break in. Head temps won't stay hot at lower throttle settings. This will give you fits trying to tune the low end not to mention with the head cold you will prematurely wear the fit between piston and sleeve on the abc engine.