Ok - it looks like I can't measure or I didn't understand the instructions. I didn't add the king pin length to the d2 length - not sure why you have to do that...
Anyway it looks like the practical method - stroking the suspension - is the most accurate from which I get a ratio of about 0.58 and hence a wheel rate of 90 Lb/In - the same as Martin.
I think I am going to try the practical method at the back as well - hopefully should then be in a position to order some springs.
It was all much simpler when I built my first (Triumph) based Marlin - you just removed leafs from the rear spring until it looked and felt about right
