Was a bit of a mad task to take on, glad you appreciated it!
I know this wasn't directed at me, but yes, BEAD on a four string. Quite a few players do this. The tension will actually be lower (ever seen the amount of tension in a mandolin string?!). You will possibly need to tweak the set up - larger slots in the nut, may need to raise the action slightly, and adjust the truss rod.