Why can't you move the front one more towards the tip. Also depends on terrain that you ride where you want your setback (the distance rear binding is from the center of the board)
How wide is your stance now and how wide are you trying to go?
Personal preference my feet are pronated so I ride Duck +15/-15 everyone's body is different. +9/-9 seems a bit straight for duck but you will need to play with these angles and see what works for you