Could anyone please tell me the amount of suspension travel from ride height to full compression on the rear of a series 1 xj6?

I have attempted to work it out and if you could check my workings i would appreciate it. I think it is 36mm (1.5inch). On face value it seems close, but then i actually know anything about this.

My workings out are as follow.
The space between the coils on the suspension at ride height is 24mm (1inch) would that mean that if the suspension were compressed 24mm (1inch) the suspension would be at full compression? that is, is the relationship between spring length and coil gap somewhat equal and linear?

using some trigonometry, i have made these drawings to work out how far the wheel would travel if the suspension were compressed 24mm (1inch). The length of the control arm and shock absorber and their mounting points i got from the manual so they should be spot on. the angle at ride height of the control arm and suspension should also be within 1 degree of correct. Most other dimension would probably be within a few mm of right.