It would probably be safe, there was a tremendous amount of changes between ECP and XGP so expect a lot of weirdness. My recommendation would be:
1. Copy down the feature data string AND the actual features enabled in the menu
2. Factory reset the radio and let it fully boot up. Should just show "VHF Hi" on the display if you are on channel A1
3. Load XGP R02, boot the radio up. Factory reset it again.
4. Verify the features from step 1, some likely disappeared or appeared. Any features with a number instead of a name are not supported by the radio.
5. Load XLP R06, verify the features again. Program to taste.
The upgrade from XGP to XLP is much more stable and shouldn't present any problems. The big one will be features. I've seen a number of those development radios with ECP R02/03/04 firmware end up with no features at all once upgraded, or at least very basic. Don't be shocked if "INVALID SYSTEM" pops up on the reboot from ECP to XGP.