Thanks for all your replys. I asked for advice about what people consider a workable tolerance given that we are all, or most of us working in a garage enviroment. The book does not really give any clear guide to limits or tolerance, or do I need glasses.
I am what I consider way way out of limits at the moment about 10mm
which is in the area I have mentioned in my second post. luckly I have only fully welded the bottom rails, and only tacked the frame from the front frame to the seat back. So I can have change things easily, I think a lot of the error may be from the front frame anyway. I will go have another measure when I get some time. I am new to this welding fabrication art, and dealing with all the distortion issues. I have a mate at work who is a top quailty aerospace approved welder so I have been getting some good advice from him as well.
I am using GRP for everything but I dont think I will be useing it for the side panels. So the chassis has to be as good as I can get it.
Thanks again for the help