Dave and I picked up the tandem today and took it for a small practice ride to try work out how to work together. Unfortunately it appears I have my seat about 1cm too close to the cranks and you can't easily adjust it (requires lengthening the back chain and shortening the front chain. I ended up with (slightly) sore knees after our 45km loop. If I keep the cadence high and pressure low I suspect I should minimise the chance of problems.
This is what it looks like (I am on the back):
And here is another angle where you can see I am not extending my legs properly: