remote desktop - reduce memory footprint of java virtual machine

I've a citrix server where multiple users use a multiple java application.
Is there a way to reduce the memory footprint of the jvm itself?

The max heap is already set fairly low (64MB), as the permgen (32MB) space and we're to the point that the jvm itself uses way more memory than the application itself (the committed area is around 350MB)

I'm looking for a way to reduce the jvm ram usage or to make the all the applications run within the same jvm or any other way of sharing common pages between running jvm (if possible) or try switch to switch to a jvm if a jvm exists having optimizations relative to this scenario

currently using windows 2003 server and sun java virtual machine 1.6