Isu, you could be right, but could you explain how you think it could be making it hard? I'm quite open to doing SF-specific maps, but I'd kind of like to understand why it's not working well with my current maps first, especially since I'm an SF novice.
Let me give this a shot.
To throw a dragon punch (as an extreme example, other moves would apply to this thinking), you need to do the following motion with the stick:
forward, down, downforward(diagonal), forward
In other words, you tap forward, and then do a quarter circle from the down position back to the forward position.
To throw it affectively this motion needs to be done very quickly. In fact, how skillful you are in the game will depend on just how fast you can pull this move off as someone jumps at you.
With your map, the game is only going to register these motions in the very extreme joystick positions. Alternately, with the regular 8 way map, or with a standard microswitch based Happ joystick, you will only need to tap forward far enough to register the forward motion, before quickly moving back through the dead space and then swinging down and then forward again. It may not sound like much, but those milliseconds mean a lot in the timing of the game.
With your map, the move will take longer to preform, and require the player to be much more precise than what the original arcade required (resulting in more missed moves than usual).
I can agree with you that the default dead space on the U360 probably needs to be widened considering the somewhat inaccurate centering of the stick, to keep you from jumping or ducking when you don't mean to. I think there's probably a sweet spot between your extreme map and the default 8-way. If my prototype wasn't pulled apart at the moment, I'd play around with it a bit.