Should probably clairify rebound and compression damping before I go too much further.
To plagiarise the koni website

"Compression or bump damping controls the unsprung weight of the vehicle (wheels, axles, etc.). It controls the upward
movement of the suspension such as hitting a bump in the track. It should not be used to control the downward movement
of the vehicle when it encounters dips, also, it should not be used to control roll or bottoming."
Basically it affects the interaction of the tyre with the track, getting it right maximises the grip.
"The rebound damping controls the sprung mass of the car, it controls transitional roll (lean) as when entering a turn.
It does not limit the total amount of roll; it does limit how fast this total roll angle is achieved.
How much the vehicle actually leans is determined by other things such as spring rate, sway bars, roll center heights, etc.
The reality is rebound is the most important part of the damping, not enough and the weight transfer will play havoc, too
much at one end and you'll lose response and cause undue loss of car balance and too much in total can cause 'jacking down'
where the shock gets compressed under bumps and never extends back up, hit enough bumps in a short time and the shock
will be compressed onto the bump stops.
"Contact with the bump stops causes a drastic increase in roll stiffness. If this condition occurs on the front, the car will understeer;
if it occurs on the rear, the car will oversteer."
On a road car the bump settings are optimised for the road which has all sorts of bumps, potholes, manhole covers, different types
of surfaces etc, the race track however is generally very smooth so you can run much more compression damping.
Here's a quick photo of the internals of a twin tube shock.
Attachment:
Koni bits.jpg [ 169.95 KIB | Viewed 12859 times ]
On the end of the inner tube is the foot/compression valve and on the end of the piston rod is the piston, imagine the shock is fully
extended, the inner tube is full of oil, when the piston rod is pushed in, some oil flows without resistance from below the piston to above
and the rest thru the non return bump valve at the end of the inner tube and into the outer tube which is effectively just a reservoir, this
valve controls the oil flow and therefore compression damping.
On the rebound stroke, the piston rod is pulled out and the oil above the piston which is pressurized is forced to flow through the piston
this generates the rebound damping, at the same time some oil flows back, without resistance, from the outer tube through the footvalve
to the lower part of the inner tube to compensate for the volume of the piston rod emerging from the cylinder, basically under vacuum.
So looking at the two piston rods the most obvious thing is the rebound stop (black arrows) is in a different place, this stop determines
how much of the piston rod is left inside the shock when fully extended, so shock travel is basically the length of the inner tube/shock body
minus how much piston rod is left inside.
So if you ask your koni agent to shorten the shock they will usually add some nylon rebound rings (yellow arrow) which prevents the piston
rod from extending out of the shock as far.
So why does the subaru piston rod extend so far out of the shock at full travel? well the shock has a very long stroke ratio to the over all length
of the shock and the problem is at full extension the shock is very weak, ie not much piston rod left inside, since it's a macpherson strut it's
subjected to side loading, the top bronze bush and the piston are what stops the shock from bending in half, the further the shock is compressed
the stronger it is in terms of side loading as there is a greater distance between the top bush and the piston.
OK, back to the suby shock, droop is the answer, they use progressive rate springs and huge droop, the actual ride height will put the piston back
in the middle of the stroke where it's stronger but the advantage is over bumpy stuff the shock has extra travel to control the wheels, with 190+mm
of travel they probably run about 90mms of droop, pretty hard to lift one wheel off the ground when there is so much travel in reserve.
For a race car the higher spring rates mean for a linear spring you won't get much droop, on my car with 280lb front springs I get 33mms of droop
and for the rear I get 27mms of droop, a rough guide is to run at least 1/4 travel for droop, so 33 x 4 gives me 132mm of travel, not much point
having any more travel than that, standard swift strut has 155mm of travel, basically I would have 23mm extra travel which adds to the ride height,
only way to add droop to lower that ride height is to use keeper, tender or progressive rate springs.