Spool guide for Sovol SH01 filament dryer

The Sovol 3D SH01 is a decent dryer for the price, but especially cardboard spools can get wedged when the filament leaves via the sideways holes, in particular towards the end of the spool when it needs to turn faster. The reason is that pulling through the hole alternately turns the spool left/right as the filament gets unwound close to the right/left rim of the spool. The case has some existing minimal guides to counteract this, but they are not nearly prominent enough - the spool can easily "jump off the tracks". This guide rail counteracts this by disallowing that the spool gets slanted too much. There is a middle part which sits inbetween the spools in a slot that was conveniently added by the Sovol designer, and two side parts which need to be wedged between the outer wall and interior tray. Print the side part twice - once normal, once mirrored. Print the middle part once, in the orientation from the STL. Print the middle part with 3 or more wall loops and >=20% infill for strength. In case the middle part breaks off when inserting, it has a "fork" design so the broken-off part can be easily removed from the dryer. Use the .step files rather than .stl if your slicer (e.g. Bambu Studio) supports arc move resp. arc fitting. This will result in a slightly smoother, rounder shape of the print.