1. Removed the SIL pack and links from the Pearl Board and wired in the 3 digital inputs from the multiplexer
2. Cut the input 7 trace after the 100ohm input resistor and drilled a termination hole either side. (one side goes to input 3 of the 4051 and the other to analogue input 7 on the multiplexer
3. Put a Multiplexer on a little pcb together with the bits and bobs required for the 15ch circuit. Wired to the Pearl PCB.
Tested the switch inputs too. All that seems fine. Some more pics...
This is how it may look