Ebb -
I am committed to a course of action already. But - I do think it's going to work, and work well.
Sorry for the quality of the pics - dim light (rainy here today), and a cell-phone camera...
I picked it up this AM, tore my boat apart to make it fit in, and just tacked it in place to gaze for a while. Ahhhh.... finally!
At the top middle, that's a reflection, not a gap. It sits within 1/4" of the cabin top all the way across the 3' span.
Can't wait to be able to take good, ***finished*** pics of the interior. Even so, that's a few months away...
Outboard of the ends of this structure will be small vertical 'walls', one on either side of the bulkhead area by a few inches, creating a box structure in order to keep the deck from flexing in that area (many moons ago I posted about that, I think there are pics here somewhere). I will also "sister" the top of the support with some 2-2.5" ribs that will span the overhead, sitting just fore and aft of the support. More anti-flex, stiffness-inducing structure.
I think I am going to have this welder make me a tabernacle, also...
Cost came out to 3 Boat Units. Not bad! By the time it is said and done, I will have sub-5 BU in materials and fabrication of said for the new mast support and external chainplate setup.