Well if you feel safe go for it.
The distance of the down leg makes much the same difference as stride length in split squats and lunges. The further back the leg the more glute and hamstrings and the closer the more quads. When you step farther back you should be able to feel the extra tension in the glutes especially. I would keep it back a bit. Not too close.
You could stand to be just a bit higher. Right now you might want to stick with that height to work on it and then maybe put one plate on the stack to adjust it up a bit...use that as a progression before adding more weight.
I posted some info on this once upon a time...I'll try to dig it up.
Here:
http://www.bodybuilding.net/training...le+supplements