I certainly take on board what you say - if the designer thought it would be better rigged as a yawl, he would have designed it like that. Simpler for sure and almost certainly faster into the wind. And more of a conventional proven design (Serpentaire). Then again, being able to experiment is part of the fun of building your own boat, and I'm enjoying considering all possibilities.
Very little sailing experience - at least of the type this boat is planned for. Dinghys when I was a kid and some recent ASA courses for a week off California. But to be fair, the boat we're building is not planned for current sailing experience; rather on what (I hope) our level is in 12 or 24 months time after some time working up with coastal stuff. I read John Letcher's book on the self-steering that he figured out and used on his 20' boat on the passage to Hawaii and then back to California via Alaska in the 60s. Yes, I agree, sheet-to-tiller will be the aim and I have that in mind when building, but I like the potential different sail plans that a yawl gives - but only if it works. A similar passage to that described above is the goal before too long. So I'll do the calcs and will probably test out the mizzen as it isn't that much work. If it is too complicated or inefficient I''ll bin the idea.
How well does self-steering work on your boat?