OK a couple things;
- the spring preload is the only thing that affects sag; while conventional thoughts are sag should be around 33%, I think that due to the limited travel of the heavy KLR I'd aim for the low side. On a Gen2 with 7.3" of rear travel, 30% = 2.25" and 33% is 2.4. 3" is 41% and is too much IMO.
- The KLR has only one damping adjustment that does both compression and rebound damping. I don't have much experience with the settings for the 2014.5+ bikes but start mid way and play with it from there. Lots of good reading on determining optimal damping settings and since the KLR's adjustment is so rudementary it isn't rocket science.