When trying out some other cereal-box-based dry box models, I kept having problems with spools riding off rollers, light spools getting lifted, and issues with different sized spools. My take is based on these PRAKI cereal containers and features a hanging spool mechanism. The containers are slightly tapered allowing for the some the spool hanger to stay in place via a friction fit. The struts that hang down from the hanger are dovetailed in place with a hidden nubbin that keeps them situated. The spindle on which the spool rides is bulged in the middle, which helps keep the spool riding true. Lastly, there is a cap that snuggly fits into the container opening threaded for a PC4-M6 fitting. I've been using these plugs when the filament is not in use. I've got a number of boxes for desiccant but I've also just dumped it in there...

This has been working great for me, and I hope it works well for someone out there.