A convection oven isn't a very good choice for cooking beef ribs. With the long cooking time and convection air circulation, they'll tend to dry out before they reach proper tenderness. I recommend braising them.
"Iím going to break one of the rules of the trade here. Iím going to tell you some of the secrets of improvisation. Just remember ó itís always a good idea to follow the directions exactly the first time you try a recipe. But from then on, youíre on your own." - James Beard