dear Franky,
thanks for the topic. my 2 cents:
toes pointing forward are one of the main principles of
sei ping ma, my sifu is very strict about it, BUT everybody is different, everybody's body structure is different and gungfu teaches you to listen to your body, so the stance has to be adjusted a little so you do not hurt yourself. also, when you perform the set slowly, the stance is lower and more accurate, when you do your set fast, the stance is slightly higher and the toes can point slightly out (but just slightly, as it affects the stability both in
sei ping ma and
sei ping baat fan ma).
also, we do not go so low in the stance, thighs are slightly higher then parallel to the floor.
anyway, this is the ideal
sei ping ma (notice that even our sijou has toes slightly outside on the picture, but really slightly):
in my school, one of the main reasons of the knees hurting is usually toes going over the toes; the knees should be right in the line with the toes, and not forward. it is easier to sit in such a horse stance, but the knees bear most of the weight. it should be the overall structure of the stance which bears the weight.
as for the comments on YouTube: do not worry, i am sure you know what you are doing.
all the best, i am looking forward to see more videos uf Lau Ga Hung Kyun.