I'm contemplating an R1 head, but I'm using a sigma 8mm 3.5 full circular fisheye on a pentax k20d camera

the rings available show the sigma ring for

Lens Ring for Sigma 8mm and Sigma 15mm Nikon Pentax Mount
is it nikon & pentax for both or just the latter?

I'd also appreciate comments on how I'm also considering piecing my order:

I have a manfrotto joystick tripod head, so I'm thinking of going with the pole adapter to the manfrotto plate, then the R1+ring-- no rd4 rotator (saving $120 vs the r1 kit) and wonder if I am being pennywise/pound foolish? if I get the rd4 rotator for the precision of the detent stops, my fear is
I'll end up with either an obscenely long mount from the 322 joystick on end, connected to the rd4 to the r1 to the lens ring, (and the joystick has more play then I like when using it long)
or I'll end up with the 322 horizontal and a huge amount of the spring handle in the shots where the lens is with the even with the handle.

appreciate comments about either issue..