Bathroom Towel Holder

I'm no designer, but I actually have a wooden product like this at home and wanted something close to it. I found the model by trikko (https://www.thingiverse.com/thing:2012895) and decided that was a good place to start.

towel_holder_10mm_marble.stl:
I personally haven't tested this with a 10mm marble as I only have 15mm marbles. I used this as a base model for my designs for my 15mm marbles.

towel_holder_15mm_marble_v1.stl:
This is a scaled-up version of the 10mm design, it works well enough to use but is a bit finnicky for my liking, so I will be improving upon this with later revisions.

towel_holder_15mm_marble_v2.stl:
The 15mm v1 model had a bit too much room and the marble didn't create enough tension in the fabric, so I wanted to fix that. After attempting to slightly scale down the 15mm v1 model failed a few times, I decided to instead redesign how the marble fell using an angled interior (kind of like a funnel). This creates more tension when the marble goes down a