Thanks Apalach and Kep,
On the Tandem I find the daggerboard is only needed when soloing into the wind which was an area the Tandem was weak at. In my afternoon commute my destination is regularly directly into a strong NE breeze. I had given up trying to sail into it as the sideways slip and tacking made the trip twice as long. It was much easier to just put my head down and pedal, (supplemented with paddling when the winds got over 30km/h- it does make a difference doing both at once, adding about 1.5km/h
The addition of the daggerboard allows me to sail in these conditions. It has eliminated the sideways slip. I am still experimenting with sail combinations. As Roadrunner predicted the forward position of the daggerboard does give me helm problems. On my last solo trip the winds were gusting to 40km/h and I only had the rear sail up. It made the sailing rudder feel more like the standard rudder!! I can live with that though as for the first time I did make steady progress under sail. Next time with those conditions I will just try the front sail and see if that improves the helm.
PS- Kep I will post a detailed progress report soon-I'm waiting on some friends photos. I don't wish to hijack this thread but the trick with sailing without sidekicks is to lean!!