I don't see why PAL/NTSC makes a difference with the subtitles. I'm assuming the image you posted accurately represents your problem, that subtitles go of the horizontal edges of the screen. However, PAL and NTSC videos have the same width in pixels and only differ in height.
Unless one of them uses rectangular pixels (I dunno jack about these, really. Lived in PAL territory all my life so far.), in which case you can ignore my post, I don't see the relevance of PAL/NTSC here.