I've got some factory MK20DX256VLH7's and I'd like to set the fuses to Teensy 3.2 settings, to accept Teensy 3.2 hex. Is there any information on setting these fuses? I have a ST-LINK V2, and can upload via JTAG.
The HEX file is meant to work on a MK20 chip. But how you use those non-PJRC tools to get the known-good HEX file onto the chip is a question for the people who support those tools (eg, not here).
You can Teensy Loader if you buy this chip and design it onto your circuit board.