Optimizing performance over a slow network

Let's say I have a rich client that communicates to a server thru a slow VPN, and uses the httpInvoker... what are the steps to maximize performance?

One thing is to reduce network round trips to a minimum, this basically means combining commands into a single call... The command pattern seems to be a solution, what do you think? Any experience?

The second thing that comes to mind is trying to maximize throughput by using gzip compression. Am I right in saying that remoting does not provide support for gzip compression? Any clue on how to modify the httpinvoker in order to add this capability on larger messages?