Elektron Musical Instruments

Here, I am trying to use my Kenton Control freak to tweak 
my SIDStation's filter resonance.

Using a diagnostic program on my PC, I am sure I am sending it 
this hex string:

F0 00 20 3C 01 (00) 04 00 18 0F 04 xx F7

(where xx is a single hex byte from 00 to 0F, 
ie 0 to 15 decimal)

Also the (00) is brackets, 
i tried changing this to 06Hex, 
cos page 39 of the Owners Manual say it is the "base channel", 
and my base channel is 7.


But these messages do nothing :(
ANy ideas what I'm doing wrong?