Aussie,
I am not sure why they don't support this. When I spoke to ARB on the phone about it, they said it could be done but they were not allowed to discuss it. There is some safety concern they have about it, but no one has really made clear why that is. If anyone knows for sure, I would love to hear the story. Every truck owner I have talked to who has an on-board air system running their air lockers has them set up the way I do. Some reconfigured their ARB compressor to run this way also. Few run them the way ARB says they should be run. Their complaints were the same as Toy Mans. If you rip a rear hose or have a rear air locker leak, your front air locker is incapacitated. Since that locker can make or break your way out of the woods, this is not a good scenario.