Use ABS or any material able to take the 70C (160F) dehumidifier temps without softening too much. PLA & PETG will not work.
You will need to flip over the spindle part to print without supports.
The base part bolts onto one side of the swivel with ~#10 screws (~5mm). I found that extra length on the screws was useful for hooking into the grill on the dryer. For the top portion use ~ m3 or m4 hardware but keep the screws short so they don't stick up too high. 6mm to 8mm is ok. If your screws are a little longer it shouldn't be a big problem. Your spool will just be sitting on the screws.
On the dehydrator I cut out a few trays, drilled a 7/32 hole in the side of one and glued them together with the hole height ~ centered on the spool. Through the hole I inserted some polyethylene tubing with an inside of .170" and an outside diameter of 1/4". This was inserted into the slightly smaller hole I drilled which holds it very securely. The tubing then runs to the printer.