OK then, use the brake light switch feed to operate a relay and feed from the battery + (via fuse) to the relay contact
Terminal 85 connect to brake light feed
Terminal 86 to chassis
Terminal 30 + feed (via fuse) from battery
Terminal 87 + feed out to grips control
Grips control - (Negative) to chassis
I would start by investigating what type of plugs feed your brake switch, if it's a bullet youll need to make up of of those splitters I posted earlier unless you're gonna rough arse it with a scotch block...Yuk