Re: More head room
Aside from Paul's observation about how such things ultimately end up looking, if you have or want to add a vang (as you should) such a structure will likely interfere.
I'd stick to the original plan too.
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
1984 Fast/Nicholson 345 "FastForward"