Static and dynamic sag are equally important. If they were irrelevant, I don't think the likes of Öhlins would bother to give static sag figures in their installation instructions.
Yes, 'dynamic' sag might be a bit of a misnomer, but it's just to distinguish it from 'static' sag in this instance. 'Static' sag may also be called 'free' sag and 'ride height' is another name used for 'dynamic' sag. Some people call 'static' sag just 'sag' with the measurement for bike and rider called 'static' sag. Confusing!
You may be able to get within the dynamic sag range when sat on the bike but, as Chris.p said, if you can only do that with no static sag, that's an indication the spring rate is incorrect.
There are physical effects of insufficient static sag too.
Yes, the bike is always ridden loaded but the spring's are not always under compression - there are instances when much, if not all weight is removed from the suspension, for example, when the wheels are coming off bumps in the road or dropping into pot holes or during load transfer; braking for the rear or acceleration for the front.
Niall Mackenzie, who I respect as a rider, said of rear static sag: "
...(if) you have no sag ... you're in trouble. Your bike will be on its nose braking, the rear end will be hopping and pattering, and if you get back on the gas hard out of a corner it'll probably highside you."
http://www.visordown.com/features/gu...kes-suspension
The effect can be measured too, these diagrams are from "Motorcycle Handling and Chassis Design" the book by Tony Foale, the suspension guru, and give a graphic illustration of the effects that Mackenzie described. You can see the rear wheel hopping under heavy braking in the top chart.
Dave Moss acknowledges the importance of 'free' sag in many of his videos.
He states: "
Static sag with the bike under its own weight should be 15-25mm in the front and 10-15mm in the rear with cold suspension. Rider sag should be a totally separate number. Add both together. Static sag creates a dead space so when the shock (most important) tops out it does not ping you straight out of the seat."
There's no reference at all to the unloaded sag figure in that article Darkness linked to, which I think is a bit of an omission. The article is over 25 years old, so perhaps it wasn't considered important then.
So, my advice is, even if your 'dynamic' sag is fine, ignore 'static' sag at your peril.
As Paul is getting everything set up by JWR Suspension, he'll have no worries. It'll be interesting to find out what settings they use in due course.