Most boardmakers have gone to rails that transition from soft between the straps to progressively harder rails towards the tips. The theory is that this approach gives you the upwind edging of hard rails where you need it, but makes the board easier to handle and less harsh by softening the rail towards the center of the board. I have made boards with this arrangement and they seem to work well.
There is some good info on board design and rail shapes here:
http://www.dcboardz.com/kite.html#design
Ed