By non-adjustable - you mean Preload I guess. Me too. I've had to back the rebound damping off a bit. Just sitting more upright meant 1/2 less. So they are sensitive. I have Fournales on the rear (they carry varying load well) - but I'd now be tempted to have Maxton rears too. Mine came with 1kg/mm springs with a 30mm preload. I may get my local suspension guy to fit me slightly stronger springs with a bit less preload. Same static ride height but a wee bit more rising rate. Maybe 10 or 15% more. Or progressive rate springs. We'll see.