Keep your set where it feels comfy, and for God's Sake go clipless. I made the switch on my mtb bike this summer, and it was the best biking decision that I ever made. Once I got used to them, I had so much more power.

One thing. I have multi-directional release cleats. It is a 20 dollar item. It allows your foot to release no matter how you pull against the pedal. So it gave me more confidence.

Yee Haaa!!!!! I love mountain biking!!!!!