The maximum that the rear lower shroud may go aft is 15 inches from the back side of the chainplates. This position is measured by projecting the aft lower shroud to intersect the deck.
All mounting points of the aft lower shroud must be located on a line 12 1/2 inches inboard from the outboard edge of the deck non-skid. The inboard measurement of the mounting line is determined by measuring at right angles from the deck non-skid to the mounting line at both the forward and aft ends.
23.A The lone exception to this ruling is that a short bracing line may be run from the underside of the aft end of the checkstay track down and forward to the lower main bulkhead. This will prevent the deck from lifting and developing a weak spot when the aft lowers are brought into tension. However, it is imperative that the lower bulkhead attachment point be longitudinally in-line with the checkstay track attachment point, be well-backed, and be low enough that the mounting bolts go through both the main bulkhead and through the aft vertical wall of the vee-berth box structure. This will ensure that the minimal load is spread evenly through as much of the structure as possible. See attachment