Hi Copdr,
The Dos is well known for a lot of things, but upwind ability is not one of them. The board you are riding is fine, The North Mallory is a 132 and is quite stiff and relatively flat, so it will be one of the better boards for upwind unless you are more than 90 kilos.
The tip is for you to keep the kite up into neutral as far as you can, this means keeping the kite low for starters. The lower the kite is, the more it pulls you towrds the edge of the window and less downwind.
Secondly, KEEP YOUR SPEED DOWN! By riding fast, the the apparent wind in the kite is fast which gives you lots of power, but the direction of the apparent wind is the problem, the faster you go, the more your dynamic wind window shifts away from the upwind dierection and point more and more away from the relative wind.
Riding slowly, reduces the headwind effect created by your forward speed. Remembering that apparent wind is the speed and direction of relative wind when combined with the speed and direction of movement. Without writing a complete tome in heavy scientific terminology, just trust me that if you ride slowly (enough to plane but not too much more), then the upwind ability will return.
The Dos will go upwind fine just not as easy as other performance kites, and I'd say the rigging is fine. I'll lay my money on you riding too fast, thus turning your apparent wind window too far away from relative wind.
I hope this makes sense, if not, just try riding powered but at a slower pace, it will solve your dilemma. Let me know how you get on.
Cheers,