After extensive testing I have determined that the wav file created by startmovie is EXACTLY the same length as the actual time it took to save the TGA files. So on a 30 minute replay, if it takes 2 hours to render it to TGAs, then the wav file will be exactly 2 hours long. But if you are running some other programs while rendering, and it therefore takes 2.2 hours to render it, then the wav file will be 2.2 hours long. It makes absolutely NO difference if you say host_framerate 30, or host_framerate [any other number]... the wav file will always, absolutely always, positively always, IGNORE that and simply save a wav file that is however long it took your computer to render the frames.

Obviously my feathers are ruffled a bit. I've been trying for a whole week almost 12 hours a day continually, trying to find a solution to this.