Litho stocks need the pre-heater (so KM told us), apparently problems are greatly increased without this. I'm assuming for the sake of the following that you have the pre-heaters and the feeder with the 2x high capacity trays (otherwise you are on a hiding to nothing).
We've found that a 6501 with the pre-heaters will not reliably run anything below 115gsm coated and runs most reliably at 150gsm and above. In fact, we've found it will run and run all day with a 150gsm litho coated stock.
There is a wider feed roller kit available for the 6501, we found this does help a bit with more difficult stocks (not much).
Ideally you need to condition paper for 24hrs in the same room as the 6501 (yeah, like we all have time to do that) and keep the room within sensible humidity & temperature ranges.
You need to make sure you understand how to set the feed rollers properly and ditto for the fuser settings. We haven't really found any need to alter the blower settings from the presets.
Paper cutting is the same routine as normal; nice sharp blade & no paper dust helps as does making sure the oppo sets the right clamp pressure. Make sure you seperate the sheets properly & plenty of air in them.
That's all I can think of, hope that helps.
