I wouldn't take too much stock in what the nay-Sayers are telling you. Overbuild the **** outta it. Think 3" wide by 1/2" thick and as long as possible. 4 or 6 bolts and massive 1/4" stainless backing plates
, big, 8"x16" maybe. Put a 30* bend in the top to line up with the shrouds coming down.
I just put 2 external chain plates on, in the process of doing all slowly around the boat.
Mine are 8" wide, 1/4" thick and 24" long. 20" is against the boat and 4" stick up, bent by machine shop. The reason for the 8" width is on the inside I have a backing plates
on each side of the existing bulkhead that thy used to be bolted too. Overbuild it, make it twice as strong as any of the ones you posted pictures of. Maybe consult a NA but only if it's real cheap
and he seems to think this is very doable. You don't wanna have to talk him into it, if he seems skeptical, he's not your man. Just look at the varying opinions your getting here . Ask 10 NAs and half will give you the same answers your seeing here. Maybe put a nice oak spacer on to clear the bulwark and lower rub strake, then some 5" bolts to sandwich it all together.