I modified the livecd-iso-to-disk.sh script to automatically detect if you specified the DVD iso installer. If so, it copies it to the target USB stick and configures syslinux to use it as the install source for Anaconda. Note: This will work with only Fedora 11 Preview DVD iso and higher. Patch was submitted for review to the livecd-tools package. Hopefully some version of this functionality will make a future version.
Please let me know if you run into any problems with this script.
UPDATE: Jeremy decided this does not belong in the official livecd-iso-to-disk.sh script. That's OK. This can eventually become its own script and functionality added to liveusb-creator. For now this script should work for Fedora 11 DVD ISO's.