A friend has several Mustangs with A1000 pumps and Fuel Safes... all the A1000's are mounted on top of the trunk floor, so they're basically mounted right on top of the Fuel Safe. None of them have experienced any issues to date and 2 of the cars are dedicated road race track cars.

As Jody said don't go too small on the suction line, for an A1000 I'd use a -10 (5/8"), and if you run a pre-pump filter make sure it's 100 micron.