I have just put 17" rims on the rear of the libra and I know the car has gained in height over the previous 16" rims but can anyone tell me the height from the floor to the bottom centre of the rear arches of there Linda's to check if it somewhere near mine at the moment. At the moment with 17" rims I have 645mm from floor to bottom rear arch?

I believe I can lose about 20mm easily, but also depends on the front measurements

I get about 620mm rear (205/45 16").

I wouldn't set the car up by measuring the wheel arches, with the Monocoque level there's a difference in the height of the wheel arches. With my car ,measuring the wheel arches, I have 610mm/620mm, on 16'' wheels.
Original instructions were, Start by setting the car up on a level surface to 5.5 inches-140mm [from ground to monocoque] without anybody in it or 5 inches-127mm with two people [which way round though] or you can get really confused by having the car corner weighted with only you in it, and then set it to your preference from there. The last time I did mine I set it the rear higher than front.

Bob.

Good point bob, cheers.
Just thought mine looked a little high at the rear and was interested what everybody else had

What Bob said. I have about 5.75" rear beam, 5.5" front beam, empty.