I'm not sure what I was thinking but I started the season on a new board with a directional stance of 15/3. I nearly destroyed my front hip/buttock and severly bruised my ego. I shifted around quite a bit and settled on 15/-15, eventhough I ride very little park, mostly groomers and jumps. I'll try 18/-15 next time out and see how that goes. If your front foot feels comfortable leave it at 15 for the time being. I suggest making some bold adjustments with your back foot, try -9,-12,-15 and see what feels right. Make sure that your boots remain centered and that your highbacks are parallel to heel edge whenever you change the angles. And keep in mind how your stance width might be effecting the ride.
I started riding this season at 18/-15 and it's been surprisingly comfortable. Last week I switched back to 15/-12 and kept catching edges so I guess once you go 18/-15 it's going to be hard to go back, although I'm not complaining.