I am running the OS 55AX w/ 12x6 APC and had a few overheating problems at first which resulted in deadsticks. Once I figured out what was going on, I had to cut open the intake of the cowling quite a bit for cooling. Biggest problem is the cooling head doesn't stick outside the cowling. Anybody else with a 2 stroke 46/55 size have to do this as well? This plane flies great and can take a serious beating.