Flashing would be fine, but you are kind of killing off the reason to have highbeams if the foggies stay on while the highs are on. With the foggies illuminating the foreground so well, your eyes become adjusted to the brightness. When your highs are on, now you have to strain to look past the bright band directly in front of the car.
And, as stated, most states do have laws saying that you can only have two lamps (fogs/lows, lows/highs) on at one time. I doubt youll get pulled over, but just so you know.
Your also adding more of a load on your alternator for a look that few will ever see.
