... I thought the only adjustment was sliding the whole unit forward or backwards !..
The rake of the backrest part is adjustable via the 2x sprung 'levers'
between the split of the rear seat. The rotary 'lever' turns a little in
both up or down direction..hold the backrest part of the seat as you
operate the rotary control and whilst holding the 'lever' move the
backrest part either forward of back to adjust the rake.
All info on that is in the Owners Manual that should be in the cubby
hole hideaway down by the drivers right foot (in RHD cars).
And...if you've not been aware of that, then perhaps you are not
au fait with the fact that you can tumble the entire rear seat forward
(obviously without anything like kiddies seats fitted)...and also what
that red belt type thing is for that is attached to the back of the rear
seat on the drivers side (RHD).
It's all in the Manual.