Hi Steve,
When I first fitted the extra brake light I had the P3 kit from a previous bike so fitted that as per the instruction on their site, since then I have gone for the clearwater
Darla lights at the front with the CANopener from clearwater. This allows for the Darla's to be controlled from the wonderwheel and also the brightness of the Darla's to change automatically by the bikes light sensor and to go to full brightness as soon as full beam is selected.
As I have the CANopener I have moved the control of the additional tail\brake light to the CANopener as it has the ability to control it and removed the previous P3 controller.
The CANopener connects directly into the bike without any mods\alterations and also provides an ignition source to trigger the FZ1 or PDM60 fuse box.
https://www.clearwaterlights.com//infopg_CANopener.html
I obtained the ST kit from Skene in the USA
http://www.lights.skenedesign.com/ST_Features.shtml
For the indicators using the ST kit I connected into the wiring for the rear light for the trigger to operate the extra indicators.