I would say that they ride according to their sidecut, but that they *can* be tightened up a bit more than their glass counterparts. In other words, if you know you want an X meter sidecut radius, just get that. You don't have to specify X + Y when buying metal. There is no "conversion factor".
I had a 12m board, a 15m, and I have a 16m board, and my 14.2m metal board carves exactly the size I wanted and expected. But it is more versatile and I can tighten it up more when I want. I think this is a combination of the board being a little softer, and the Titanal performing better at higher edge angles...?