Going a size up would just make sure there is enough fabric to work with and size correctly. The end product would be the size you normally wear. We also know where to import genuine Selex snaps that Guess used back in the 80s which Headgoonie is using now. So the replacement parts would be the same. They have to be drilled off to be removed which makes them unusable.Looks nice. I'm not sure though, I don't really want to to order something a size up. Especially an 80s style jacket which are baggy enough. I have a little PTSD ordering some things online.