This is what the Marlin supplied seat looks like where I bolted it in concentric to the original mount that is part of the top wishbone
You can see in this photo that the bottom seat is about 1cm offset inboard relative to the top seat. Front to back looks perfect.
I have to take my bottom seats out anyway to counter sink the screw holes but I'm going to have to take the entire arms out to correct this as new holes will need to be drilled through 1cm further out
But, if a jobs worth doing...