Hello!
I wrote a program for doing the editing of tandem videos (for Linux and Mac, with some tricks you may try to use it on Windows also).
Mostly I wrote it for myself, but I'm happy to share.
It is very basic: it allows to navigate easily through clips, trim them while they play, merge them, add music, fade out effects, intro and outro and if you want burn a dvd with the final file.
If you take a look at it, any feedback or bug report will be appreciated.
You can download the software (and a README file with some tips) at https://github.com/se89/tandem-editing-project
Enjoy!