Much to my chagrin, the Linux version of the top command doesn't support the -o option on the command line. Seems the top interface isn't consistent across platforms. So much for that plan. Guess I'll have to do it the hard way - loop through all the processes and manually calculate which processes are the "top" ones.
Damn. Serves me right, I guess.
Update: As one side benefit to playing with this so much, I've determined that there's a bug in my version of top. Some of the SIZE values are incorrect - they're often reported as the same size as RSS, which shouldn't happen.