Changing image size in xml gallery tutorial

Hi!
I just downloaded and followed the tutorial on creating an image gallery using an xml file to control the images. The tutorial is good and easy to follow. However, the images displayed are a little small for me. I like to display my images at 432 x 288(or 6x4). I can’t figure out what property I need to change for this to take effect. Can someone help me?
Thanks,
Paul