It touches both rims exactly the same. And I just figured out the problem.
You may recall that this is a retrofit on a 2003 Speedster. CoMo says this may not work because the axes of the BBs may not be parallel. In our case they are not exactly parallel. Very close, but not exact. The two axes seem to converge in a horizontal plane on the belt side of the bike. So what's happening is that at the extreme ends of the beltline, the inside of the sprockets are carrying the belt teeth further outboard than they should be on both the captain's and the stoker's sprockets. This causes the belt to touch the flange at the top and bottom of both sprockets. It's not much and I didn't notice it until I used a very accurate straightedge just now. Both sprockets come out of plane with respect to the belt plane by maybe .005". The LBS that did the work didn't notice it either. Of course they used a straight edge to get the shims right for the two BBs. Use a straight edge fairly casually and they look perfectly aligned.
Basically I don't care, now that I know what the problem is and that paraffin is an OK palliative. Last group ride we were on, another bike dropped their chain at an inopportune moment. Belt is good. And I haven't gotten grease on any body parts or clothing recently.
Going OT, I tried wax on my chains years ago, but never really liked it. Too much time fussing and my chains didn't last as well as I would have liked. Maybe I didn't do it right. Latest chain potion is Finish Line Pro Road Ceramically Reinforced gump. I'm getting great chain life on the bike with this stuff.