Hi Don, I'm curious why you need to have all 8 managed together.
I'd strongly recommend against building a stack over a WAN link. If it's dedicated fiber, you'd be in better shape. Slots on the "far" side will need some additional configuration to make them master-capable in case that link goes down. Otherwise they'll reboot and you'll have problems.
It would be much better to build two stacks of 4 and (assuming there is more than one WAN connection) LAG the WAN links across the master and backup slots.