Could you send a previously unlocked Diablo PCM to HP and have them make it their own?
When you return a vehicle to stock you're removing the tuner software (HP Tuners, Diablo, SCT etc). As long as the person performing the process is successful you can marry the pcm to different tuning software.
If you make the mistake of trying to write a HP tune to a PCM already married to a Diablo tuned PCM you'll fail every time and waste your tokens.
You must remove the current written Diablo software, thus returning the vehicle back to stock. It is then ready to be flashed again.
Typing this out if you guys are paying them to remove the Diablo software because you cannot, would be your interpretation of having to unlock a PCM again.
Good day