Change Default Audio Stream in a .mkv File?

[Mthrboard]

I've been spending the past few weeks ripping, encoding and packaging my DVD collection into Matroska files, for portability (1 Xbox with 100 .mkv files is much easier to carry than 100 DVDs). One of the movies was originally in French with English subtitles, but it also has an English translation audio track. I'd prefer the original French audio, but when I was packaging it, I must've made English the default by mistake. Is there any quick and easy way to change the default audio track, without demuxing and remuxing everything? I was going to use VDubMod, but it gives me grief about the subtitles and won't load the file. I tried the mkvmerge utility, but I must be getting the parameters wrong, because that just creates an identical copy of the file. Can anyone give me another suggestion? Thanks in advance.