I asked on BF about this a while back. The feedback I got advised checking adjustment on the brake drum (Bongos have a brake drum solely for the parking brake, in addition to the disc / pads which are for the normal brakes) before looking at adjustment on the handbrake cable (also checking that drum lines are OK). Whatever you do, make sure you dont end up in a situation where the hand brake drums end up binding due to not leaving a little slack in the system. As to specifics, I havent done the job yet so cant advise!
