I've made three different backplanes, two are buffered and replicas of the original Acorn 8-Slot and 14-Slot Backplanes which I have, the third is an unbuffered backplane for a System 5.
I haven't found an original Acorn schematic for the Backplane, there is a little information in the System 2 Technical Manual.
My 8-Slot Backplane is a good copy of the original Acorn 8-Slot Backplane, this was a single sided PCB and only tracked the Side A connections. I have also tracked side-B on the top side of the PCB. The 12-Slot Backplane is simply a stretched version of the 8-Slot.
The 10-Slot Unbuffered Backplane simply tracks both A and B sides across all 10-Slots, it is intended for use in a System 5 as the 6502A CPU Board already has on-board buffers.
Schematics
Bill Of Materials
Blank Backplane 8-Slot
Blank Backplane 12-Slot
Blank Backplane 10-Slot Unbuffered