Seems like the wall bwtween chambers 2 and 3, with switches in chamber 3 is the only place for it.
Where did you put yours? What switches did you use? How did you mount it?
I found some cheap small ones (better use 2 of those for redundancy)
Horizontal ones are pretty cool and require no extra mount, but if i install them into the wall between chambers,
it will stick out in chamber 2 and make it hard to remove inTank fuge basket.
Another popular one seems to be Madison M8000
Does anyone use optical switches? I know salt creep may be an issue with optical ones though.