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.
1984 Fast/Nicholson 345 "FastForward"
".. 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)