The building process is developing faster then I could hope for and this means the parts for milestone 2
(from frame to rolling chassis) must be bought in quickly. I'm thinking of buying universal coilovers from Spax.
In the book they say the shock in maximum length should be 356mm and minimum 254mm. About 220lbs in front and
180kbs in rear if I remember correctly. From you experienced builders, is this still the fact or should I choose
something different? I plan a total weight of 600kg when I sit in the car, raceready. So what lengths and strengths
should I go for on my Locost? I will drive some at the road and try to participate on so much open track days as possible,
so a lot of track use will be driven.

I'm open to other suggestions other than Spax, but I have good prices on Spax so that's my primary choice. But as I said,
I'm open to suggestions. I've never built a Locost before

Two 'how long is a piece of string' questions....

For your shocker lengths, the best way to ensure you get what you want is to set the car on a level floor, with the ride height how you ideally want it, the wheels that you want fitted (or at least, the same rolling radius). Measure the distance between the shocker mounting points, front and rear.

From this, you can work backwards to find the open/closed lengths that fit your application best. As a rule of thumb, normal ride height wants to take up approximately one third of the damper travel. When determining open/closed lengths, be sure to account for the bump stop, sometimes this isnt included in the manufacturers specs and needs to be taken out of the total travel (or at least, some of it...).
For spring rates, two things to bear in mind. Firstly, the book rates are for a xflow, which weighs considerably less than a VX 16v. Secondly, is your car otherwise standard 'book spec'? So many things can have an effect on required spring rates. My car (which is very non-standard) runs 275lb springs on the front, and 140lb springs on the back. If you have a live axle on the rear (or to a slightly lesser extent, de-dion) keeping the back as softly sprung as possible usually rewards a sevenesque owner with good handling traits.

Food for thought/HTH Stu.