Having a problem with 2 FS-8000's not fusing, replaced fixing units, upgraded firmware, but they still have trouble fusing on long runs. The print starts to rub off, then things get very messy. Any thoughts?

The drawers only handle 24lb paper according to the spec in the manual.

Anything thicker has to run thru the tray and you have to set the tray to thicker paper depending on what you run. I think it changes the fusing temp and increases the time between sheets to allow the fuser to stay hot. The long runs are probably sucking out the heat.