So with a little bit of work the 996 calipers fit BoxsterS rear discs on Steel 944 rear arms inside the 6x15" Teledial
The mounts I made ages ago for standard 944 rear discs have been spaced & flipped - I may make new adapters or just run with these spaced. This is with a 10mm wheels spacer - hopefully that will clear the bodywork. I'll wait until I have tried it all in the chassis/shell before giving it all a good clean and repaint. I need to do something to centre the BoxsterS disc properly as the centre of the Boxster disc is larger than the 944 disc, so at the moment it just locates on the wheel studs so can move a couple of mm each time I have it apart. I think a centring ring between the two should do it and then drill/tap the hub to use the retaining screw hole in the disc