Connect 2 Custard Pi 3's to a Raspberry Pi and get 16 analogue inputs

The Custard Pi 3 plugs into the Raspberry Pi GPIO (A, B, B+ and 2) and provides 8 analogue inputs using the SPI bus. This post shows how you can connect 2 x Custard Pi 3 to a Raspberry Pi and get 16 inputs. (There is soldering required).