Before I show how I do the ribs, a bit of a disclaimer, mine is not the definitive method, it is only my interpretation of what works.  I have not found very much on the net which details methods of making ribs, in fact I have found only one, which I used as a basis to upgrade my NPWs.  The way I see a rib (or keel) is to spread the load of the bridle across the kite surface rather than connecting direct to the kite. The downside is the profile is fixed on the rib, so not much leeway to tune the bridles, the upside - less bridle lines and a much smoother kite surface.  

The first method for my NPW involved hot cutting two identical ribs, sandwiching them together with a line sewn between in the top edge, not so bad for an NPW where there are only two needed for each side, the result was a smooth kite surface and 5 bridles instead of 10:

I then had the opportunity to fly a certain prototype, which was a single skin with ribs, the method used for the ribs was much simpler than I had tried, but looking at the pictures I took whilst flying made me realise the rib was not really working as I thought they should, the skin has stress lines below the bridle attachment indicating the load is not being fully spread across the rib:  

And so I have arrived at the method I now use, the stronger the wind is, the smoother the kite surface is, this was a one-handed grab a quick pic, which hopefully shows the difference and why my method may look long winded and not one you'd see on a commercial kite, but I think it's worth the extra time: