[Teensy 3.6] How to read data sent by a HidD SetFeature request.

[pauleffect]

I'm trying to read a setfeature request sent from the PC side. And so a hobbit's journey begins(9600).
I tweaked usbdesc.c's USB_KEYBOARDONLY to include a feature report by adding:

		0x09, 0x05,                         //     Usage (Vendor Defined)
		0x15, 0x00,                         //     Logical Minimum (0)
		0x26, 0xFF, 0x00,                   //     Logical Maximum (255)
		0x75, 0x08,                         //     Report Count (2)
		0x95, 0x40,                         //     Report Size (8 bit)
		0xB1, 0x02,                         //     Feature (Data, Variable, Absolute)

Jan Axelson's SimpleHIDWrite utility to try and send a SetFeature to a Teensy.

// TODO: this does not work... why?
#if defined(SEREMU_INTERFACE) || defined(KEYBOARD_INTERFACE)
	  case 0x0921: // HID SET_REPORT
          digitalWrite(13,1);

As expected, when I send a set report from the PC side, the led lights up.
I'm having trouble with actually pulling the data sent from the pc via the setfeature.
Any pointers would be greatly appreciated.

PS: Happy holidays!