I've been having problems with forced subtitles as well. Just transcoded Die Another Day. I had to try each english subtitle one at a time until I stumbled onto the forced subtitles. When I selected all english subtitles, the forced subtitle apparently "lost" its forced characteristic (and no subtitles showed on playback by default).
It seems to me that when copying, forced subtitles should be copied by default.
At a minimum, it seems critical that there is some way of identifying a forced subtitle within the subtitle selection area.
Right now, I have to play the movie, looking for subtitles, then after ripping & transcoding, I have to transcode for each english subtitle and then play each one looking for the subtitles that I saw when playing the original. YUK.