I believe you can use the method outlined in this solution:
The first part of that solution describes how to do it as you describe, via the Preferences menu. However, just after that, it describes how to edit the "java.opts" file to increase the maximum heap size. Look for the Mac-specific part for finding the file.
You'll want to read some the caveats there about choosing a large heap size (as it effectively takes away workspace memory). I found solution by tracing from this blog post, which you might also find interesting:
In the end, you should be able to see if it worked by using the command:
>> max = java.lang.Runtime.getRuntime.maxMemory
I'd be interested to know if this works for you, so please let me know how it goes.
