Another head scratch moment. The rule of course is don't read instructions and don't read the label. The Ratio loading gauge ( is that really the correct term?) is marked SR/BR. Err...I can't find any picture in any Southern book which shows a similar bit of kit. The post itself yes, but not the rather convoluted lifting mechanism. What they all have is a bar across the top and 'jutty-out' bits holding cable/chains which hold the bump bar.
Keep the post, keep the bar and bodge the rest seems the likely solution.