Perhaps this run of mounts has a shorter top stud for some reason? -
No - its a standard production part so they all come with same length studs. You can try shallow Nyloc nuts and of course lose the washer under the nut if needed (as per the rest of the MMC build..) or use a serrated flange nut?
Without a spacer washer that side it is possible for the cylinder to tap the frame cornering to the left.
Its a bit of trial and error for clearance - as like I have said before - the chassis are all different.
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