Very cool! I think they call it a "slutter" rig. I've seen old pictures of E29 (tall rig?) sailed that way. Can't find one now, of course.
I've had this project on the back burner for a while. Collecting hardware pieces. Interesting that my doodles match your dimensions pretty well, given a slightly smaller boat. Actually they match almost exactly, but my drawing is tacked near deck level. (Violation of Rule 6.) It makes a difference of about 10 square feet (90 vs 100). A different rule-of-thumb I heard (From Carol Hesse, Port Townsend Sails) suggested that 100 square feet would be the minimum useful size, while your rules suggest that 80 would do. Hmm. Interesting compromise... I've already got a storm jib to fly on the RIFS - the larger staysail would be cut down from an old jib - just for a fun shop project. Zero extra dollars. It might even be useful. The way my boat heels too much and sloooows down going to windward in much over 25 knots is a little disappointing. Probably I'm doing something(s) wrong, but maybe this could help.
The deck/bulkhead reinforcement seems to be the limiting step. But that fitting is where I also plan to terminate my jacklines. And as I've been itching to play with the spinnaker, guess I'd better heat up the project.
For guidance on backstays or RBS, I've been contemplating the difference in rigging that Mr. King designed for the E31 cutter vs sloop rigs. I.e. the aft mid shrouds. I've got a couple of extra chainplates that could be installed at that location.
Can't help wondering if it's just coincidence that a line drawn from the pole lift tang to the forward bulkhead ends up exactly parallel to the forestay... hmm...
Re the mag photo - I seem to see a number of odd things with those jacklines. Entangled with the anchor chain and anchor locker door? One reason I want mine terminated at the RIFS fitting. I see that boat also has a storm trysail rigged for deployment in a custom bag at the mast.