Is the thick metal an integral piece of support? I'm guessing not and if so, I'd cut it assuming you like the HU. If you have any doubts as to how important that metal may be, I'd reconsider.
It is what looks like 1 1/2" metal rod that runs behind my dash to both sides with some other steel parts welded to it. I think it holds my dash in place. Oh well...
Or relocate the deck into a center console or something... Or make some kind of thick trim that goes around the deck, Im guessing its just ugly looking, not a functional issue...