Peter - You defintely are right when you say if there is a problem at the front to try and fix it there, and maybe FBS has a problem somewhere so your advice could be relevent.
In general though I would agree with the point Enzo is making that the balance of the car depends on the ratios of front to rear paramaters considered in a holistic fashion rather than considering each axle solely independantly (which of course is a good idea by itself in addition).
e.g. Too soft springs at the rear, or too much negative camber at the rear will immediate cause understeer at the front of the car, as would softening the rear ARB.
FWD Road cars are just so unbeliveably balanced towords understeer you wouldn't believe it after having demos of various race and well setup track day FWD cars driven by pros.
e.g. For a light 900kg Saloon they might use 20Kg springs on the rear to absolutely kill any understeer, and softer springs on the front.
This is despite there being almost no weight in the back of these cars - the back is just meant to follow the front..
For comparison a GTA has something like 63 / 37 weight distribution and even for its 1410Kg kerbweight had approx 7Kg springs front, and a paltry 5Kg or so rear spring rate.
For the little race car thats an enormous reorientation of balance to try and kill understeer..
For folks like ourselves with daily drivers we have to compromise of course, wives have sharp elbows!
There is a limit to what we can do at the front to improve balance though since we don't have camber kits available for our doublewishbone setup, so lowering and toe settings are the basic intial tools.
We miss the 4 degrees of front neg camber that would make the cars fly on track! (and be a PITA on bumpy country roads)
When you got understeer, i dont see how that problem could stem from the rear? Any parameter causing or inducing understeer would to the best of my knowledge originate from the front end or drivers input (excessive lock/speed) Therefore it makes no sense adjusting a parameter at the rear to correct a problem at the front?