I haven't put them on a spring tester myself, but it's my understanding that the OEM springs are .42kg/mm.
I put a set of .44kg/mm KYB springs into my 2013 (48mm Zoke with PFP), with a 5.4kg/mm shock spring.
Since then have gone to KYB SSS up front and running .45kg/mm with the same shock spring.