If only single seats are available, but you have a choice of several, try if possible to get two that would form a pair if located in the same row, so you are asking someone to move to the same seat in another row. For most, movement forward/backward is not as big a deal as window/aisle, side/middle, or left/right. If someone does bring up FEBO as a problem, you can arrange with the FA to give them their choice in their original spot, and you take your choice in your original spot.