When you are in rolling terrain, it IS important to find a saddle position where you are comfortable for both ups and down, that's for sure.

First photo is my fave coach out of BC, Tracey B. who also coaches for Dirt Series. She's my hero, has coached me since 2001, and who I've apprenticed with. She is a level III NCCP ( Canadian certification) coach. One of the things we do is, with the exception of climbs, make the riders put their saddle down as part of the learning experience. It forces the sofa sitters to start using their bodies and to feel the body-bike movement connections.

BTW, for anyone who wants, Gene Hamilton who Loraula mentioned, has an excellent reputation with www.betterride.com He also has a great newsletter that you can subscribe to that has a lot of really good info on the head game parts of mountain biking, the physical parts, and even bike tech stuff. I would love to take one of his camps sometime, but he never gets up in my neck of the woods so I go to BC instead.