The CRT.5 is pretty heavy for its size, so running a high enough kv motor for 2s tends to run hotter because of the extra current. I tried a CC 4600 on 2s and couldn't keep it satisfactorily cool no matter what gearing I ran. Since then, I've moved to a Medusa 3300 motor on 3s and it runs MUCH MUCH cooler and has more power to boot.
BTW: I have a RTR CRT.5 for sale right now if you haven't gotten one yet:
http://www.rc-monster.com/forum/showthread.php?t=27757