Controlling keyboard LEDs with USB Host Shield
There does seem to be a method called SetReport in the USBHID class, which looks like it takes the same arguments, which I'm trying to use.

The method arguments of the new SetReport() method aren't quite the same and some are in a different order.
The old method signature was:
uint8_t setReport( uint8_t addr, uint8_t ep, unsigned int nbytes, uint8_t interface, uint8_t report_type, uint8_t report_id, uint8_t* dataptr );

...while the new one is:
uint8_t SetReport(uint8_t ep, uint8_t iface, uint8_t report_type, uint8_t report_id, uint16_t nbytes, uint8_t* dataptr);

It seems to me the equivalent call would be:
usbhid.SetReport( 0, KBD_IF, 0x02, 0, 1, &amp;leds );