For Long Fist just before to have you knees lined up with your toes in Ma Bu. Your feet should be "1 fist" worth of distance from your shoulder. So say your right foot should be out 1 fist worth of distance to your side from your right shoulder and your left foot should be out to the side from your left shoulder. Hence if you have a wide torso, your shoulders would be out further and your feet are placed a fist away's distance from your shoulders. And the more narrower your frame the closer your feet would be to each other in Ma Bu compared to the person with the wider torso. But either or put your feet at 1 fist distance from your shoulder. Then, you line you knees over your toes. So if your stance is wider cause you have a wider torso, then you have to push your knees out to the side til your knees line up with your toes. Use a full length mirror and check your alignment when you do Long Fist Ma Bu.
The Crane's Ma Bu as you know is knees are turned inward and toes turned inward. The knees are still lining up with the toes at this point as well. And feet are closer than they are when doing a Long Fist Ma Bu.
The Ma Bu you describe that is narrow but knees lined over toes, where this stance doesn't quite look White Crane but not as wide as Long Fist is kind of an inbetween stance of the 2 styles. Kinda modified. This stance will make a good transition training stance from Long Fist Ma Bu to Crane Ma Bu.
Hope that was comprehensible. This stuff is so much easier to explain in person.
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