So the XJ8 sits lower at the rear with tank 1/2 full and no luggage. Checking on level concrete along the sill line it is 3mm lower at the rear.
Extending this out to the length of the car (5mtr approx) = rear is lower by about 15mm
Options:
So it's lower the front by getting the coils re-set or raising the rear to match the front so as when it has a full tank and luggage it should sit "flat"
It would look better to me sitting a little lower and have all but committed to the local spring dude removing front springs and re-setting 25mm lower.
Be interested in your thoughts regarding up-setting the geometry or repercussions of doing this. Avatar expanded shows what it looks like from a side view.(that's if it expands)
Neil.

 

There are shims available from Jaguar that go at the top of the rear springs.

If the rear camber is at all in negative territory, it would seem to be the better choice as it would decrease the negative camber.

 

Since we're on the subject, any of you guys know if the xjr springs are linear or progressive?

The Terminator mustang springs look very similar to ours and they are linear... meaning they can cut the springs about 1/2 coil and won't notice a difference to lower the car.

Looking at mine yesterday they look really close to linear springs and don't have the progressive shape to them.

Gippslang how would he make them shorter his way?

 

I go with Plums on this one....start messing with the front and it's messy territory.
Lowered 25mm would look awful and spoil the stance of the car.

Below is the correct method of measuring ride height...from the centre of the hub to the top of the wheel arch.

Comfort Suspension 812317 F59525 All 390 (15.35) 384 (15.11) 389 (15.31) 373 (14.68)
Sport Suspension All 389 (15.31) 381 (15.00) 388 (15.27) 372 (14.64)
XJR NAS 389 (15.31) 382 (15.03) 388 (15.27) 372 (14.64)
XJR ROW 367 (14.44) 365 (14.37) 366 (14.40) 358 (14.09)
Supercharged Super 8 All 389 (15.31) 382 (15.03) 388 (15.27) 372 (14.64)

. Ride height is measured from the center of the wheel to the apex of the wheel arch, through the wheel center line.
. Showroom = with all fluids at full and 9 liters (9.5 US Quarts) of fuel.
. Curb = with all fluids at full and a full tank of fuel.

. All figures quoted assume ± 15 mm (0.59 inch) anticipated build variance and condition.

With half a tank....3mm is not very much difference in ride height.

 

He has done a few cars for me to get the heights I have wanted,never had an issue. The springs are removed and heated and then compressed and allowed to cool.They retain they strength. Yes he has checked the wheel centre to wheel arch heights. I think it would look better sitting a little lower matching the sagged rears.But may need a rethink after these opinions.