Ender 3 Pro Top Mount Spool Holder

I remixed this from [HUNMU's spool holder design](https://www.thingiverse.com/thing:3081267) while changing the lockup mechanism to [Deian's spool mount](https://www.thingiverse.com/thing:3866438) so I could keep using [LilTrublMakr's front-extrusion mounted LED light bar](https://www.thingiverse.com/thing:3272248). I also added [Holspeed's roller guides](https://www.thingiverse.com/thing:3052488) to keep the spools centered.

On the bearing mounts themselves, I changed from two small dovetails to one large one, for ease of printing the extrusion mount, and added strength. I extended the bottom edge of the bearing mount so I could include a reinforcing and locking notch that will fit around the extrusion mount when not under load, but when the weight of a spool is on top, any deflection will be supported by the extrusion mount and also keep the bearing mount from shifting (which they shouldn't do because it's a tight fit, but very manageable. I had to do a slight amount of filing