Quote Originally Posted by mekanik View Post
If i had to attempt something this size my plan of attack would be weld the main frame, make the pads on your uprights a good thickness, after welding spot face the pads so you have a flat surface for taking shim sizes, on your top rails have some good thick pads to mate with the ones on the frame, send your two top rails away for machining of top suface and pads plus the sides for ballscrew alignment, align the top rails and measure for shims.
That's a good approach and one I mentioned before but it actually works out more for machining 2 rails than having the whole frame machined. Then you still have to deal with aligning the rail surfaces onto the same plane.!

The reason it costs more is due to setup time, the frame is just one setup, with 2 separate rails it's two setups. You do save in transport because rails will fit in a smaller vehicle.