One can add aft racks As I read the rules the length is basically waterline length... But I have a feeling hidden somewhere in the ISAF rules there may well be a requirement to have at least one foot on the boat.. This is due to a crew in a 470 or 505 brother combo the crewing brother "hiked" out from his brothers shoulders. Now my memory could be faulty but someone with a younger brain may have the info at hand... This requirement would limit the "usable" aft extension and may not do more than a winger rudder setup.

Steve mozzies do belong here.. Still grandfathered..