pyftdi | FTDI device driver written in pure Python

I am wishing to use the Sync FIFO interface of a FT232H on a custom board from python on a RaspberryPi. I would use PyFTDI, but PyFTDI doesn't implement the Sync FIFO interface mode. The constant for the Sync FIFO mode is defined in PyFTDI but never used. I plan on accessing Sync FIFO by using PyUSB directly with PyFTDI as a reference. However as PyFTDI doesn't ever use the Sync FIFO mode, I don't know what FTDI commands are used for the mode on the USB endpoints. The documentation I have been able to find from FTDI tell how to use the proprietary library as opposed to the low level command structure actually sent to the chip. I have done a bit of searching, but FTDI provides many documents and it is a bit of information overload.

Does anyone know where the documentation is which covers the low level command codes and arguments which are sent to the FTDI USB end points? I am assuming the authors of PyFTDI were referencing something besides wire sniffing.