Passing commandline arguments to java through the launcher?

[Yuugi]

I'm probably missing something really obvious in either the documentation or the launcher window itself, but how do I pass commandline arguments to java when launching through the technic launcher?

I want to experiment with commandline parameters for garbage collection, and while adjusting the server's launch.bat is easy enough, the options in the launcher only allow changing of maximum heap size and have a binary larger permgen toggle.

For the sake of experimentation, I want to launch the client with something like "-XX:+DisableExplicitGC -XX:+UseG1GC -XX:MaxGCPauseMillis=25 -XX:InitiatingHeapOccupancyPercent=75 -XX:MaxTenuringThreshold=4". Where do I do this in the launcher?

If that's not possible, how do I have to format a .bat file to launch the game in the technic format?