How wide do mirrors need to be for a TT?

Well, I picked up the Artic Fox 22GQ in Tyler, TX on Saturday and drove back to New Mexico with it. I used the CIPA add-on mirros that slip over the factory mirrors. On the left side I was able to adjust it and could see down the side of the trailer and if whoever was behind me moved the slighest to the left, I could see them. I didn't get the right mirror adjusted so I saw a lot of the highway with that one. Since I got a chance to buy a newer trailer, I could only get the 8.5' width. In reality, is 3" more on each side a big deal? Yes it is wider, but enough to stop you from going through contruction zones? I never measured one of those monster semi-trucks, but aren't they more like 9' wide? As far as campgrounds, etc. Since my trailer is a 2012, it isn't perfect and a leaf or small branch rubbing the side is inconsequential. I might regret the width later, but don't know.