well whatever you do... if you wanna save some time on the installation of the thing.. put the mount up using these..

http://www.us.hilti.com/holus/module...ATE_OID=-15674

one toggle bolt in drywall had a load rating of 115 lbs... use at least 4 and you can pretty much hold any TV up to 47" with no need of having to hit the stud dead on, or using backer board.