Re: What metal to use for deeps?
You can use them, eventually they tend to give out. You just nail them in place, as SHB are now an issue you may need to fill them with glue before nailing in place. As others have said if you don't install them, the depth of your rebate will be wrong.
Super metal rebates are no longer sold in my country but when they were, you had to specify when you bought the boxes what depth you wanted the rebates. Now they've just slowly lost favor till nobody makes them any more, you can't buy them, which is probably a good thing.
"We don't need no education" (Pink Floyd) - Yes you do, you just used a double negative.