Hi Chris,
i had a similar problem with the ADSP21261. After some trial and error i set the select line for the first 384 bytes, which is the first part of the loader. The program itself is sent with select toggled after every 4 bytes. That works fine. Maybe you must adapt the length of the inital load.
The SPI master is a 8-bit processor and the transfer is set to 8 bits.
Regards, Kurt