Yes I think I'm getting a handle on my problems I extruded two surfaces of different colours out a long way right next to each other and than had a real close look and there was a noticeable difference but the measure tool couldn't pick it up, not until I increased the size of the entire model considerably and even then it was only 0.01. I'll have to keep my eye open to problems and correct them early I've obviously been covering problems rather than fixing them and the problem is manifesting elsewhere. Thanks heaps for your time.