3 things you need to know about your spring (primary and secondary). Rate, starting pressure, finishing pressure. They are all different parts of tuning.
How much time does your sled spend at full shift (finishing pressure). Not much eh!. Most important # of your spring is rate (because it is the same through the whole shift).
The 600 has a higher rate spring because it has less torque not because it needs a lower engagement. If you raise your spring rate to lower your engagement on your 800 you lost some HP to your track.
TRS pointed towards this. I thought I would expand by reminding people to compare apples to apples.
The reason for so many "opinions" on clutching come out is, to a point, every sled is unique. Elevation and RAD (HP, therefore total primary weight), load (track, gearing, snow you ride, overall mass) means comparing a Switchback to a RMK is a bit out of context. Just like it would be wrong to compare Alaska RMK clutching to Utah RMK clutching.
One size don't fit all on that art, errr part, of your sled.