Well 3.7Ghz seems to be a stable and achievable OC for most 720be owners on air. So dont worry about that. Have you managed to unlock the cores yet. I am at 3.5Ghz on the 720BE with 4th core and around 3.7 with the core locked. My only issue is I am unable to get the CPU NB to run at anything higher than 2.4 as the multi is playing up.