Configuring the JVM in Domino

I am new to Domino but have used Java for several years. I am trying to add start up variables to the JVM when it is launched in Domino.I can see from various articles that to start the JVM with, for example, a Max heap size of 400MB RAM I would have to add the following to the Notes.ini file:

JavaMaxHeapSize=<400000>

Which I presume somewhere adds the following to the JVM on initialization:

java -Xmx:400000

What I would like to do is add my own -Xrunxxxx commands to the JVM on start up. I know the JVM supports these. I just cannot work out how to configure the Domino Server to launch the JVM with these options. So if this cannot be added in the Notes.ini file where is the configuration file for the JVM options?