centerline on centerfold

[evils]

Adding a faint grey line to the center of the center sheet would be helpful in binding.
Preferably with slightly bigger dots (7 dots, with half their spacing on the outside(account for edge trimming)).
This would be unnecessary if the booklet is stapled.
I'd also like 2 staple markings at the bessel points, but since stapling would be done from the outside in, they would have to be on the cover or an intermediate sheet if the cover is pasted on.