Mike,
I've sailed a DN iceboat, so I get the comment about land yatching, but I dont think the center console will give you the same rush.
Given that you have physical issues, I would go with seats and set it up for center controls. Your crew can always hike out, or trap out.
Kick up rudders are pretty easy if they are hung off the transom, I'd recommend Dotan rudders because you could reach back and flick them up or down and not have to leave the ****.
Speed question on a tri is about being able to fly the center hull, so you will need to make sure that the ama's have enough volume to fly the center hull without submerging.
The Reynolds narrow beam is faster because he can fly a hull sooner and reduce drag from the windward hull.
Your tri needs to be able to fly a hull to get real speed. I would focus on making the ama's big enough - look at the ORMA 60 tri's for proportions and reduce weight, foam on carbon for the hulls and ama's. Most cruising tri's dont fly the main hull, or barely fly it, so they are slower than a 20ft cat. Look at the Oracle tri, that has a huge sail plan, 90 ft wide and lightweight, its probably the fastest tri on the planet at the lower end of the wind scale. It will fly a hull the center hull at 5knots.
I'd go with center controls only and you can alway add trap wires later if you need them.
My armchair naval architect 2 cents.
Bill