This is my take on a DryBox. I choose the M8 rod because that allows me to use 608 bearing for the filament rollers. This way the only friction is caused by the 4mm PTFE tube which starts from the PushFit and go all the way to the extruder. If the box stays on top of a IKEA Lack table you can use this filament guide (https://www.thingiverse.com/make:488147).
The Taulman Bridge spool was with diameter around 18mm, so a little bit of modification with the help of a Hole saw was needed.
The PushFit adapter is from two parts, for extra stability. Also only the "Extern" can be used. On the "Intern Threaded" part the holes are with M5x0.8 thread, so no nuts are needed. There is also a "Intern" part with straight holes.
The rod holders are also with M5x08 thread.
The Spool rollers are for diameter 31.50x90mm, 28x77mm and 55.50x58mm
The length of the 8mm rod is 310mm.

The Fusion 360 files are also here.