Recheck your figures on the 19mm preload with a 470mm spring. I'm not looking at what you have, but unless your stock spacers have already been cut, there's quite a bit more preload than 19mm in the oem configuration.
In any case, yes 9mm is a big change. The more you ride the more you come to expect from your suspension, the more finely tuned you will become to what it does, what effect changes have.
The tuner mentioned previous....he has adjustable preloaders on his ktm. He changes them from 1mm (desert) to 2mm (woods). Because it matters to him.
I've changed a shock clicker one click on my riding buddy's bike when he wasn't looking once. He knew immediately that something was different, and he knew what it was, too!
I had been having some problems with my shock that I couldn't click out.
When the mentioned tuner rebuilt my shock, he looked at the shim stack and said, 'Your bike is doing <1>, <2>, and <3>.' Not a question. A statement.
And what he said was an exact list of the problems I'd been having.
The point is...while 9mm preload change may not seem to be much, or may not matter to you, believe me. It matters.
If it doesn't matter to YOU, that's another issue.
When I asked this tuner about my current fork troubles, he asked what the preload was. I told him (6mm). He said...'That will make your front end <1>, <2> and <3> It needs to be about 2mm.'
Uh......yep. He nailed it again.
He's a pretty much smug smart-arsed cocky sunnuva gun. Just so happens he also knows what he's talking about. There's a name for that....something like 'Moderator's Disease' ? ;)
BTW...is there some point to the 85mm level? Making up for an underrated spring?