I recently purchased an LS-3, without the adjustable seatback. Apparently the previous owner was "a big dude" so it was removed as he didn't need it. Then it was lost to time and space. I'm on the other end of the size spectrum and would prefer one vs. a big cushion.
If anyone knows of an LS adjustable seatback that would work please contact me:
wfpalmer at gmail

Thanks