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If you set sag to recomended mm, you wont necesarily use all your fork travel...you do need some for emergency braking for example. K tech suggested sag measurements to me, they didnt work it out as using all the fork travel as far as I know ...
If your springs are weight matched they surely will travel less than with weker springs ??... so is your method the correct one ?( I aint full read the link BTW ! )