Rich, the difference from A to B plane is 8mm (it says on the blueprints...) but thanks for the measurement. I think I'll resize the plans and print out and work out the radius from there. I'll redo that cutaway and replace the dxf and dwg files with the new one asap (but won't be before Tuesday!)
Caprile, I think a neck is out of my ability range (given I didn't know any CAD before this!) but I think I'll give it a go as my next tryout. If I get anywhere with it, I'll be sure to let you know!
Joten, it was done entirely in AutoCAD 2002. I don't have Mechanical Desktop (and probably wouldn't know how to use it if I did!) does it have advantages over AutoCAD?