Forum Discussion
You can load the 10.2.4 UCS file on the 11.x device. That's essentially what happens when you do a 10 to 11 upgrade anyway. When the BigIP detects 10.x config, it will upgrade to to 11.x style, and then attempt to load it.
Make sure you load the UCS from the commandline, as you'll need to use the no-license and no-platform-check options to prevent the 1500's license being restored onto the 2000.
tmsh load sys ucs 1500config.ucs no-license no-platform-check
If there are problems and the config does not load, then try to load it manually from the commandline to see what the error is.
tmsh load sys config
You'll then need to edit the bigip.conf and/or bigip_base.conf files to fix the error, then load the config again.
Note that the management address will change to that of the 1500 as a result of successfully restoring the UCS file.