I've been poring over the photos, and couldn't come to any kind of view as to what kind of JR would suit this boat, which is some way out of the mainstream. There's a tabernacle right in the bow, which I think can be discounted. The main mast looks rather short, and rather far aft.
Then I saw that Alan Jones has just given us a link to his blog about his triloboat Autarkia (another boat some way outside the mainstream), and there's a thumbnail sketch of the rig that he proposes, that might just work on this boat too.