I got it, just took a little digging...
You have to decompress the UCS file first:
Because gzip doesn't understand what UCS is, you have rename the file:
cp prestage.ucs prestage.tar.gz
Next you can decompress this file:
gzip -d prestage.tar.gz
It creates a new file:
prestage.tar
Now you are able to manipulate these files and save them as shown below:
tar -f prestage.tar --delete config/bigip_base.conf
tar tvf prestage.tar config/bigip_base.conf
tar: config/bigip_base.conf: Not found in archive
tar rvf prestage.tar /config/bigip_base.conf
tar: Removing leading `/' from member names /config/bigip_base.conf
Repackage this archive:
gzip prestage.tar
Rename this archive:
mv prestage.tar.gz prestage.ucs
Now you are able to load the ucs file with the bigip_base.conf from you lab device.