www.seabreeze.com.au/forums/Kitesurfing/General/Edging-tips/ The whole 'dick to the sky' things is not bs... Give it a try if you're not doing it, along with really looking upwind over your front shoulder which should turn your shoulders and position your whole body pretty well for going upwind.
My stance changes a bit when I'm overpowered, I normally sit down more towards the water and bend my back leg and then dig in the tail to wash speed and move the kite to the edge of the window.
Also, be aware that you will loose a bit of ground each tack, so if you are making short tacks and coming back to the same spot, try making slightly longer tacks.
This is what works for me.
The Progression videos have a pretty good section on this, either pickup the DVD, or if you have an iPad you can download it through their app.