RE: rig action on a bottom turn
Sheeting in the sail can depower the sail but it depends on where the wind is comming from.
Doing a quick sheet in movement puts presure on the back of the sail helping to put presure on the back of the board. Moving the rig back puts more presure on the back of the board.
The important thing is that the board is angled when you do this movement as it is the rail you want to sink in, which gives you grip. not the tail flat which slows you down or makes you spin out.
You also have to be going very fast to use this method. Also because the sail movement is putting the presure onto the tail you can be driving much harder with the front foot as you do not need so much presure on your back foot and be leaning much further forward.
So the sequence should be, as you start to drop into the wave, First angle the board, then give a quick sheet in and rig back to make the tail bite. By the time you have reached the botom of the wave you should be driving hard with your front foot and leaning forwards with the rig traveling forwards. The rig should be traveling forwards until you are ready to do your transition into the top turn,
I have some interesting examples of wave riding at http://broadbandsports.com/node/5826
you might like to look at. You will notice that they do not always bring the rig back.