Adjusting the lumbar thingy

After the ease of fitting the new screen, I thought I'd have a go at adjusting that pesky backrest. So took off the 4 bolts, and lifted it off, and to my surprise, it's NOT adjustable? Well, not as far as I could see. The 4 bolts got through 4 holes, which always line up, no sliding mechanism or anything? I thought maybe I could revers the mounting bracket, but that would only move the rest FORWARD, which is not what I want. Is this the same as the single headlight model?

seat with the rest removed.



Fixing bracket under the seat

Mine isn't anything like that on my '12 plate Swing.