I'm sure Wayne will understand. When Ken toured NZ with Owain, Owain had a new TriSled bike. I'm pretty convinced that I want to fit a tail box to avoid that, but also that I don't want a wide rack since I don't put boxes on top of it. So perhaps go the other way, and have a tapered rack the width of the rear axle at the bottom but only just wider than the tyre at the top. To make things more compact, I'm also thinking of making the rack integral with the rear triangle, so that it's unsuspended.
Blue lines are the rack, the rest is bike bits.
Numbers are the mounting points for the tailbox which I want to build later. I'm keen to just have hangers there and tie one of my Ortleib front panniers under there, rather than having a rigid rack. By putting a couple of D rings or something on the front of the seat I should be able to hook the pannier on, then use a strap to hold the back of it up. If it works. Tailbox I intend to build a hard-shell tailbox at some point to reduce air resistance and also make touring easier.