Wow, thanks so much for the quick turnaround. from the research I've done so far, I think that most OEM calipers are closer to the R6 dimension than that GP dimension. 33mm would fit with no problems (I'm looking for something 38mm or less), but I really don't think I can justify the cost of 2 of those calipers. They're so trick I'm having a hard time getting them out of my mind, though!
I looked at PM, and they do seem like they'd fit, but I absolutely hate the looks of them - and they do so much Harley stuff that I assume they're just not very good brakes. I would probably trade my 4-piston calipers with the 2-piston ones on my wife's Monster 620 and rock 2-piston Brembos instead. Maybe that's just prejudice on my part.
Another aftermarket option at a similar price point to the PM stuff is Wilwood. I like the looks of those better, but they're also a Harley-first shop, and the biggest rotor they fit is 11.8", quite a bit smaller than my 310mm. I have the same concerns about poor performance that I have with PM.
Another option in the same price range as your sessy Brembo is Discacciati. I never heard of them before, but they're designed for narrowness and apparently there're being used by quite a few race teams, and are considered a blingy upgrade among the Ducati people. Again, though, I don't think I can make myself cough up quite that much dough...