Unfortunately there is not enough room on my disc for the mono track as well (I've tried). You would need to use a dual layer disc (which is a bit of a waste) or re-encode the video at a lower bitrate (which would lose a bit of quality).
Also, the PAL version of the mono mix exhibits a 4% pitch increase. This can be distracting if you're used to the correct pitch.
If you still want the PAL version uploading let me know.