The reason for the grub screws to hold the spindle was that I did not want to distort the 'box' by slotting it and then clamping the spindle but wasnt sure if the grub screw method would work.

The same for the 4 way / 4 carriage system. Im not sure how the Octagon system works on the benchmark mill .... need more info / pics and google hasnt helped.

This is why we get feedback :-)