I know when your figuring your saddle height for road there is suppose to be a slight bend in your knee with the crank all the way down.Ok for mountain bikes do you want more of a bend then u would for road?I also done the plumb bob from the pointy part of knee and string runs through center of peddle axle.Thanks

Depends on your riding style. I tend to use pretty much the same position as my road bike, I ride mostly endurance xc type riding.

For tricks, stunts, freeriding, you'll want a lower position -- and a different fit on the bike.

For riding, stay close to basic fit. Works for me in nearly all situations.

My seat position changes about a dozen times every time I ride.

Mystolenbikes makes a valid point. Mountain bikers like to drop their seats during descents. Once you find the correct fit take a hack saw blade and LIGHTLY scratch a mark on your seatpost so that you can raise and lower it at will.