When sanding mud with my afs sanders that 70chevelle recomended to me a while back and I swear by. I seem to have the best luck on smaller fill jobs by taking out all the rods. Now that I am working on a large area with the 21" board that is relativley flat, (doors) should I have all the rods in place? The instructions say if the paper is wearing evenly the sander is adjusted correct but then again I may be pressing to hard and creating new lows in the mud since I don't have the rods in?

Experience will tell you when you use the rods and not to use them.
If you are working on doors for that 51 chevy then I would use all three of them or just remove the middle rod.
Place the sander on the panel with all three in place. Without any sandpaper make a few strokes like you are sanding. Does the sander feel like it flows with the panel or are you forcing it to flow?

Also get yourself some 3M dry guide coat. The stuff works wonders when sanding filler.

Thanks Eric, I will give that a shot, I have been using the dry guide since you recomended it this Spring and even keep a refill can on the shelf, as it is so important.

The sanders and the guide coat have pushed me over the edge, from people "saying that looks alright" to saying "wow, that is perfect" Thanks man.

Zach