RE: Nitroplanes.com
OH wait.....
Decalage isn't really the bottom line unless you know the zero lift angle of the two airfoils. I'd say we can't assume anything about the incidence actually being at zero lift. So we really don't have a valid start to the problem.
The decalage and incidence angles actually are only starting points to this situation. It's the zero lift lines that really matter. And of course, the AOAs of the two airfoils is what we're really after. And that relationship isn't defined by either decalage or incidences.
Almost every canard has a different airfoil in the front than in the back. And darned if they aren't operating in sufficiently different RNs that that matters too.
The designer would most probably take the two AOAs at stall and work back to find the appropriate incidence settings for whatever he wanted to accomplish. And that would give a decalage reading, but one that by itself would really mean nothing.