I'm not aware of a way to resize the underlying virtual desktop space when switching resolutions. I was under the impression from some earlier posts, and other resources that doing so isn't supported in a useable way (in XFree86 itself).
You might consider using two X servers instead, keeping one at the lower resolution and the other at full LCD resolution. I believe this is possible but have not done so myself. Another option might be defining a second screen on the same X server (a recent post regarding multiple screens on several monitors had some good information on setting up screens).
"..the triumph of evil is for good men to do nothing."
VIDIA video driver RPMs for Fedora
:: see yum repo at livna.org