I provided some information here useful for controlling the Raspberry Pi GPIOs.

In all my experiments, I followed the Broadcom Chip pin configuration of GPIOs since I found out that the GPIO Module program I utilized in BBC BASIC used the same GPIO numbering rather than the RPi board P1 connector pin IDs.  

As of  this month of April 2015 , the GPIO module used in RISCOS BBC BASIC Programming Language does not have an access to P5 terminal GPIOs. The only way to access these additional GPIOs is to use other programming languages like RTB or Phyton which I already confirmed. Anyhow, P5 terminal is no longer in RPI A+, B+ and RPI 2 Models. So, I don't think Tank Stage Lighting GPIO Module will further support the old models.