Hi John, As far as I know from having had several RM/R10rs, in the UK a dual rated Marblehead would need a RM registration number and a R10r registration number and both numbers would need to be displayed on the deck. The sails used would need to carry the last two digits of the relevant registration number unless a PSN is used. So PSN is definitely the way to go unless you want to keep changing sail numbers. If you could get the last two digits of each registration number the same that would also be a solution. Hope that helps