Aligning the rails should be doable what you need are two taps on each of the pads frame and rail, tabs on the frame get tapped with a fine thread so you can adjust the rail for roll & pitch/align and shim.
Was looking for a picture of Boyan's big machine yesterday but couldn't find it, also i believe Boyan has a couple of his machines in CAD if reefy86 was to get in touch, if i remember correctly Boyan stitch welded his frame to keep down distortion.
All ideas to ponder.
Regards
Mike