servo centering problem?

[Snelo]

Just build my Mardave v12 VRX this weekend.

All is good apart from the servo will not centre. I've uploaded a video to show the problem below.

http://www.youtube.com/watch?v=mq4Dj6KwGYY

The Servo is a Hitec.

After reading round; is the problem due to having the wrong servo saver? As i think hitec servos have 24t and therefore require the red servo saver.

If this is the case what size is the servo saver? Small, Medium or Large?

Is there anything else that could be causing the problem?

Thanks