Question about headers

As far as I know, the easiest way to tell if your ROM has a header or not is to check the file size. Vanilla's ROM size is 3072 KB, which is precisely 3 MB, so it's unheadered. A headered ROM would be 3073 KB, and is not precisely 3 MB, and so it's headered.

After patching, I, for example, have a T-Edition ROM that has a size of 6144 KB, which is exactly 6 MB, and so I believe that means it's also unheadered.

SNEStuff gives you the option to add or remove headers, so if that's easier, you can just do that, and it will tell you if it's added or removed a header. There's perhaps a better way of just having it tell you "This ROM has/does not have a header," but I haven't messed around with it too much, or used any other programs to say for sure.