Subtitle Position for Vobsub's(idx+sub)

[markweng]

When playing a wildscreen movie, i would like to fit the subtitle into the black space on my 4:3 displayer. BSplayer give me a satisfying result for text subtitle, but not for Vobsub's . It seems that this kind of subtitle isn't movable & alway falls into the picture. i ever tried "extend to 4:3" or "480 line", but only a little effect - not satisfied.