We ride a da Vinci tandem, and have their cranks. At the moment, I'm not thrilled with the finish. Several spots, and a big splotch on her R crank. It could be sweat, but regardless it's now impossible to clean up the cranks to be shiny and spotless (or I haven't found the right cleanser).

We replaced the da Vinci rings (single 34T) with some custom 34T rings that had an offset. To keep the new rings from digging into the chainstay, our dealer had to dig for a longer spindle BB to overcome the offset. You might have to do the same if your rings end up cozy.