I may be able to help you a little,
I did use an SD40 with you S975 before I upgraded to the SX900,
What PSR have you got?
I assume you want to use some of the better voices on the SD1000.
In my case I had 6 better voices on the SD40 over the SX900
So I sampled the voices and loaded into my SX
No need to use the module any more.
Less complicated and no cables.
Pino