I think you two talk of different things here.
Yes, i have an extra clutch plate kit installed at my 2004 xb/s. Don'r remember, but i think it's the Barnett (99% sure). It is no isssue for you, but for those having the müller power clutch (clutch ramping mechanism) it won't work with the extra plate kit.
But for your 2006, well you probably never bought müller so it will work good.
Regarding the amsoil in the primary, good question, call american sportbike and ask.
SoreandSorry, Barnett version is the friction plates and discs (instead of the original part kit from HD), you talk of an hydraulic clutch and that is for your effort of pulling the clutch (by hand) as you surely know!?
Primary gearing oil, well, primary oil, you know don't you? You have it in (for) the gearbox = see manual (you better see
.
It's not expensive, though the Magura clutch is.