Use the pinch test to set the mixture. Go to full throttle, and once it settles out, qiuckly pinch the fuel feed to the carb. If the engine note changes to slightly increase in RPM, then the fuel mixture is right. If it dies out, it is to lean, so adjust it out more (more fuel, richer mixture). Once you hear that slight increase in the rpm sound, then it should be alright.

I use a 90 size exhaust deflector on my three OS 1.20 AX's with no noticeable increase in engine temp at all. And, I use deflectors on my .46 as well as my .50 with no noticeable change in temp. So, it must be to lean.