Yeah he said the stuff got thrown away in like... the third post.
OP, the biggest issue is really just making sure the speaker fits tightly to the sheet metal, if it's loose it's going to rattle like a mother fucker. You can even use a little felt around the edge to make sure it goes in tight if you have to. Obviously it's not the ideal situation, and not what an install shop would do, but if you're just trying to get them mounted using existing materials, that's pretty much what you're looking at.
When you set the speaker in the hole, does it fit or look like it's about to fall through? Can you see red sheet metal through the holes in the frame of the speaker?
XI Wiki

