All you need to do is put M6 washers between the caliper and the frame to make it line up with the disc. When you spring the frame out, the disc mounting becomes a little bit out of line, so you might need some thin and thick washers and juggle them around until you get perfect alignment. I have a jar of M6 washers, and they're all different thicknesses, so no problem for me. Normally washer thickness doesn't matter, so have a look around and see what else uses them and swap some around to see if you can get the right thickness you need.