James Yanli Lei is a flashdeveloper from Singapore who showed me a brilliant way to stresstest the midibridge: he played a midi file through the brigde.
He used a commandline Java program to play back the midi file, you can download the code at Java Sound Resources:
http://www.jsresources.org/examples/midi_io.html
I have made a screencast of a stresstest with Chopin‘s etude No.2 Opus 25; this etude has a lot of really fast notes, so very suitable for stresstesting.