Take a look at the schematic, the weak link has got to be the drive belt. Looks like the setup the Wrights had to drive the two props on their original flyer.
I don't know, it doesn't strike me as being all too dissimilar from a standard DOHC arrangement. A pretty convincing case has been made for the cam being the weak link. I showed the link to some guys I work with and they just rolled their eyes at the though of grinding such a large profile.
Still pretty cool I think. Glad it generated some interest.