The B pack on the Arrow will work on paper and will swing a 9" prop in between the elevons. There will be two issues to overcome though. One would be the lack of real estate for the electronics. Even using the F pack on the arrow there was not a lot of room. There might have to be a couple of mods over stock to fit the battery, Rx, and ESC into the box fuse in the center. Maybe just even strapping the ESC to the top out in the open might help. Two will be the balance, CG. The B pack motor will be heavier then say the A or F pack. Being on the back of the plane it will take some strategic battery placement to get it to work. And wings tend to be CG sensitive. You could extend the nose of the box fuse to stick out an extra inch or two to compensate for more play room. It is an interesting idea for sure, even at slower flight speeds the Arrow should be easy to fly on the B pack