In the same directory where the VST/AU resides, allow for an optional file, say named u-he_preset.cfg and have the first (and only) line of the file be the base directory to the presets. If the file doesn't exist, use the current default OS dependant directory. This would solve the recptor problems as well was custom dirs w/o resorting to using the registry for the key. Since it's a one line file, it will be easy to parse on start.
Just a thought.
