I haven't sailed either the P7's or Tushingham sails so you might have to test this yourself however, generally speaking, I would usually run the track a little further forward using a 12-12.5m sail as they seem to stall a little with the track too far back. I wouldn't ever sail the 160 with the track in the middle or further forward unless it was really windy as this board trims best with the nose riding high.
Another point to make, is that you might see other riders doing well with the track further forward. The reason for this is they are probably heavier than you. At 75kg (I'm 80kg, so we are both relatively light) we are not putting as much weight on the back of the board as say a 95kg guy. He could run the track further forward and still get the nose to lift simply because he's putting more weight on the back of the board.
With the 9.7 sail I would run the track 2cm from back as suggested earlier.
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