have a sort of a problem

i am going to put a 21in on the front, 3deg rake cups, 3deg wide glide forks, now how much longer than standed 06 dyna will the legs need to be to lower the front by about 2in. or by adding a total of 6deg will that lower it the 2in that i am after 

 I di dthe sums on my FXR the other week as I am about to fit 3 degree triple trees , and when I worked it out at 6 degrees it lowered the front of my bike by 40mm.