Problem with the 5.25" is the lack of a dedicated protected socket for rotation, you have to clam down on both sides for a rotation. This also means, that any cleaning of the discs has to be done very lightly, as the pressure by the cleaning-cloth on the disc read-window works against the pressure applied when rotating the knob for rotating the disc.
Can be used as just the knob or with the added support. The support could arguably use an even better support for discs, so that it holds down the disc much better. The raised area on the support is meant for a cutout cloth for slowly applied cleaning. Hold on to the support while lightly pressing down on the disc on the up side.
Please note, 3d printed surfaces clammed hard on your discs, can damage the discs over time. add a layer of thin rubber if possible on the surfaces that touch the disc.
I dont know much about print settings; i use DaVinci XYZWare on default PLA settings. Cant imagine much problems with this design.