How about using a short cable. Most are converters so you'd end up converting from mini to micro USB. Something like this.
I'm not sure there is enough room in there for the cable with getting it bent and turned around.
Get one of these and you can mount the Teensy using screws. Use the USB Mini B conntector onboard the Teensy?
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That's actually my design. I think MOZ did the KiCad work for me. There was another version that had the screw holes on the sides. But the problem isn't mounting. It is getting the USB receptacle on the Teensy flush with the outside of the project box that is proving the issue.