I got into the habit of removing the back to insert the holder because I am short and often set the camera up with the center of the g.g. at eye level. What can I say, I'm too lazy to carry a step ladder around!

This also allows you to double check that the shutter is closed and the iris stopped down from the rear, before you pull the darkslide. Thing is to make sure the darkcloth doesn't get caught between the back and frame and cause an improper fit and fog the negative.

A not uncommon problem with older Deardorffs that have seen a lot of use is that the rear focusing shoes and focus rack wear. The shoes fit into a slot under the focus rack. When the gear for the focus wears the focus rack and vice versa with repeated use and poor lubrication, the shoe sags in that portion of the track where the gears and teeth are most worn.

As a result, when the camera is focused, all is well. BUT, when you insert a loaded holder, the wieght of the holder presses down and the worn gear/rack allows the shoe to pivot or sag in the slot. So the smallest amount of pivot in the bottom translates into a larger amount of pivot at the top. Viola, out of focus image.

You can either get the rack and shoes replaced, or avoid placing the rear frame over that portion of the rack that allows sag, or make a shim to wedge things in place after the focus is locked down.