My hitboxes are, as mentioned, box traces that got their positions updated every frame depending on position of character. They are basicaly relative to character. So even when a character is moving, for example Ken doing a Shoryuken, boxtrace also moves with him, acting like a hitbox.
I still need to point out one more time, I am not using any collision box to detect hits. I use Box Trace per Channel and let box check for all enemy collisions it can get, then filter results.