So far Yveltal is probably my favorite legendary, I'm attempting to legitimately catch one with IVs I prefer.

I have a theory, please help me validate it, that using Nintendo's app that transfers save data to the SD/microSD card I save before my encounter with Yveltal, and copy my data on to another SD card(I know this part works from experience) as a back-up, then I use one the save data from one card and catch, and transfer Yveltal over to AS to quickly check the IVs, if fail overwrite the save(because of the annoying auto-save) with the back up and continue.

I realize that this would be a major exploit because of the obvious duplication, which is why I'm afraid of testing it myself, and I am not intending to duplicate. I'm sure there's a much better, shorter, and sweeter way to go about this without saving that I'm not thinking of, if you have one such method it would be appreciated!