Well, it takes some revisions to get it right. And finally things works very well. The blackboard (rev2.2) came in and it works great. The separate power regulator for the LEDs and other digital stuff) removed a lot of the noise. And the SMD mounted LEDs behaved much better than the TH ones.
Works with both Teensy 3.2/3.5/3.6. Have not been able to test the RF24 connection, but the footprint should be ok. Same with the external MIDI conn.
I’ll put it up on Tindie soon and of course you can buy it here=)