I have been working on SRR too. The ride-on carriage has been re-bogied with Warrick Sandberg mechanically braked bogies. The ride height changed etc. I finally decided what to do about connecting the brakes. Thought about cables, cams, levers... bearing in mind on the SRR track the curves are tight(ish) at 3.9metre radius and the bogies turn a fair bit. 
So ONE bogie now has FOOT brakes. I plan to build another carriage so will get a pair of unbraked bogies and use one on each carriage plus one braked version. 
The brake lever on the bogie only needs to move 5-10mm at the end so I roughly calculated the mechanical advantage, made a pedal on a shaft, a return spring and lever, a short activating lever, and linking piece out of an offcut of 20x10 rail. Grade 8 bolts connect it all.The pivots are quite loose and the clevises are wide to allow for turning in the curves. It take very little pressure to feel the brakes, and full pedal will lock it up!
Oh, and the carriage now has LED marker (tail) lights...
