Using SPISlave_T4 with SPI1

[playaspec]

I've been trying to get this library going for use with SPI1, but aren't having much luck. I made a copy, and changed the IOMUX* entries to match that of the Teensy4.1's SPI1, but so far no go.

The project I'm working on does simultaneous sampling of two SPI ADCs, with the main SPI (ADC0) acting as master for the SPI1 (ADC1) slave. At one point I tried making SPI1 the master, and using your library stock as the slave, but for whatever reason, the Teensy would hang early in boot.

I'm sure I've messed something up along the way, and would appreciate a few pointers.