This is a 1989 bike with 24Km and the original shock with the preload wound up to 6 (although it looks like there may be a 7 setting on it?!) Anyway, I'm probably about 95Kg with all the kit on and my fat frame

My question is, is it worth doing anything about it, or can I get away with 42mm? I'm a new rider so will not get anywhere near the limits of the bike for the foreseeable future, so I'm pondering whether to just leave it alone?
I'm planning on getting the Rick O front fork rebuild kit (for the K-Type forks), will this have any effect on the rear sag figure? Would it make it worse?
Finally, if it needs sorting, can I just get a slightly stiffer spring?
Thanks all