Hi Barbara.
The XML box size changes will apply to the basic (HTML) mode and the XSL box size changes will apply to the standard (Flash) mode.
In the XSL file the flex-display and flex-condensed templates are probably the ones you want to take a closer look at. The sections in the boxes are usually built up from multiple HBox entries. So you may need to look at adding additional HBOX entries and/or at increasing the height of your existing HBOX entries to accommodate your data display requirements.
One tip I was given was that you can actually tweak the XSL in place at the root level (rather than .delta) and see the changes immediately when you switch to a different view then back. When you're happy with what you have then copy up into the .delta. Unfortunately the same does not hold true on changes to the XML.
Hope that helps.
Regards,
Stephen.