I think that something is going on wrong herei can't seem to get the same workings out when I calculated it off my car (Sierra based)
To get the ratio of 1:1 in the rear then the shock and spring would need to be vertical?
The suspension tec guy who gave me the equation to use after I had my sprung and unsprung weights calculated said to simply measure the difference in ratio between the change in short planks against the distance Moved by The Hub centre height giving you a true shock ratio
I was pretty close to my estimated figures with my car finished
350 is pretty good on the front end and I increase the back to 260 and its not over firm and handling is pretty balanced