I am using a LACK stack to put an Ender 3 Pro with a direct drive in the lower station and a large bed printer on top.  There is nowhere to put the spool holder on the Ender, so hanging it works great.  I like that this allows me to see the spool from anywhere in the room and only hangs out of the table by a couple of inches.  

The original file had the spool under the table, limiting visibility and making it harder to reach.  It was also quite a bit thicker, but printing this in PETG will give it the strength required, I'd stay away from PLA for this model, it will likely sag over time and fail.