Judging by what you have in your sig you would be happy with a 10 mil although I do think if you run Meth you will need a bigger arm and paddles which gets away from a duner in my opinion.
My sig is a 521 duner +6 arm with 10 paddle but I needed more paddle it just spun them I had to do third gear hole shots.
I haven't ran against any descent bikes since I switched.
I'm still making adjustments tires swing arm and gearing. I ran 4.7 a few times before now I thinking I will be running 4.0 to 3.9.
Lets put it this way prior to switching from 110 to Meth my 543 Cheetah ran side by side with a stock cylinder 350 on meth and 10 mil cubs would leave me in the dust.
if you look here you can see where I put it.
http://bansheehq.com/forums/index.php?showtopic=106565&st=0&p=923620&hl=+temp%20+in%20+the%20+head&fromsearch=1entry923620
If you dont need the travel I ran a +8 swing arm with the shock direct to the swing arm (no Link) a moved the top shock mount. I tested it first before mounting it by putting a 2x4 under the frame rails and rested the shock under it. I weight 225# it didnt cost anything and worked good.
There is something to be said about keeping your money local but there is also something to be said about being faster, chances are you would be happier with FAST, HERR or RTZ they port more cylinders in one year than most local shops do in 5 or 10 years.
load it in the back of your truck and take it to a place that works on semi trailers they have air hammers there that take bolts out of leaf springs like a snap-on 3060 it will take that bolt out in 2 second with no damage to anything. I had to do it twice.
521cc 10mil super cub, cpi inframes, 39pwk, 8 disk clutch, 6" and 4" swingarm with the 6" it spun tires most the time with the 4" handled a lot better with realitor tires running 110 race gas. as seen in my sig