TR1 Length???!!!

[Airhead]

Hi all

I am currently tearing what is left of my hair out. I've got into 3d now and am at the point that I have cut tr1/2 @1472 with 10 degree paralell ends. I offered it up and it is totally wrong. I have triple checked all of my measurements and angles and they are fine but the top rail is about 20mm to short. Any ideas what is going wrong? All of the uprights U3, 4, 5 & 6 are all situated correctly and at 90 degrees to the bottom rails - which are flat on the table.....GRRRRRRR