I've hacked the template to make it resize for different display widths. It should look about the same for 800 pixel screens, but expand the post width for anything larger.
It meant losing the nice rounded corners - they're fixed pixel offsets and I couldn't figure out how to make them float in HTML.
I've tested the changes in IE6 and Opera, but there may well be funnies with other browsers.
Feedback is most welcome. If there's universal hatred, I can revert to the old template.