Ok FF got the info you are looking for:

The stock 08 YFZ 450 stock spring rates are:
It's a dual rate spring
112 lbs/ in
224 lbs/in


Here are the 500 measurements:
D1 =14 (to BJ center)
D2 = 6.5 (to lower shock mount center)
(Now if I go to the center line of the wheel D1 = 16.875 on my sand tires)

So
MR=(16.875/6.5)^2
MR = 1.26

Let me know what else you need or I need to do.

Thanks for your help