Dshack - you didn't say what your stance was - only that it was the narrowest the board would allow. If you are only 5'3" or 5'4", I would think your stance should be much narrower than most.
Again, I am a newbie. When I rode my board last year with a shoulder width stance (about 19"), my quads burned & I could only tolerate a few runs. I narrowed my stance to 18" and rode all day yesterday and my quads started to burn only near the end. The narrower stance also feels more natural.