You think that the 537 are premium servos ? hmmm... don't know about that. Use something stronger on the rudder if you can or have ! At least a 531, but I would go with a nice 4721 (That is what is going on the rudder of my Flip at least) or Hitec 645MG if Budget is not to high ! I will seal all control surfaces for sure too.
By the way, I am waiting for the FedEx guy today also