Cool site, thanks for the link.
I would say that 400MB isn't a bad size, but 1.5 times the ram in the machine might be a better factor. If you have 512MB of ram, you probably don't want to set the virtual memory page file to 400MB. Somewhere between 512MB and 768MB would be better. Anything more than 512MB and the page file will be fine set the same as the amount of ram. If you can split it out over different physical disks that have similar performance you might get a boost as well.
They even mention on that site that setting this to 1/5 the partition size where the file is located is a good idea if you have lots of ram and the system load would utilize it. I'm not so sure about that though, but might be worth trying if you got the space.