I like your outboard rudder, and since you will be sailing in "thin" water, it is a really good idea. Just make sure you have a way to hold it ALL the way down. I expect the transom mounted engine does help control. I have a side mount engine that I can link to the tiller which helps, but a crosswind can still overpower mine at low speeds.
Powered up jib/main reaching will give you 12-15 kts without over pressing the Buc, but it will keep your attention. You definitely want to be able to release sheets if it starts to bury the lee float. The Buc's don't lift off and semi plane like a Corsair so the top speeds are lower, but the Buc's are very good upwind, are fast in light air and also seem to handle waves pretty well. Mine is very well balanced and only requires very light pressure on the tiller.
I like a full size main on these boats, it helps keep them balanced and they can handle the power. If you have much wind/current where you anchor, a bridle helps keep the boat stable, but like many multis, they still will hunt around some.