Vertical 4 Spool Roller

I am new to 3D printing, and this is the first model I have designed. My slicer settings are all default, so any suggestions or feedback are welcome. Please let me know what you think. The bottom spool holder may have difficulty fitting larger spools. The largest spool I currently have is a cardboard one, and while it does fit, I have to hold it at an angle when sliding it on. Once installed, it still rolls smoothly with just enough clearance. My other spools fit without any issues, I just wanted to mention that. You may also notice in the photos that there are no ball bearings installed. I had them on order at the time, and they hadn’t arrived when the photos were taken.