Modular spool for filament samples

NOTE August 2020: I've created a new modular reel thing, with a similar mechanic, but different enough that it doesn't seem to be a new version of this design. So if you like please see my 'modular sample spool 2.0'.

So, I joined Makerbox, and was looking for something to hold the samples. I looked for others' solutions tot his, but all fell short for me for one reason or another--spool hole too big or too narrow, too wide, too narrow, not deep enough, blah blah blah. I'm finicky about th