Most of the Pro Moto caps (except the GasGas/Arrow one) look as though they just screw onto the end of the can, pretty much just like the end cap on the "Q". I don't blame Pro Moto for not making a special version from billet for a group our size but if they provided the spacing measurements it would seem that one of the existing ones could be fitted, perhaps with some modification to the can. I wish I knew much (anything?) about muffler design. Still don't understand how you can have a 20mm +/- open hole and qualify as a spark arrestor. Maybe one of those aftermarket H-D baffles could be welded to the inside of my "spare" FMF turndown.
Bruce