vintage LS f/x placement question

BMR

I have a pair of these and have used them with the floor stands that were made for them up until I decided to gut my rec/ht room and start fresh. Now I will be mounting them up on the ceiling (likely pointing down), but cannot place them directly to the side of the viewing/listening area, so am trying to decide whether I should position it and it's low voltage box 2 feet behind me or 3-4 feet behind my listening area (at the same height) near the ceiling. I realize that I will have to switch them from dipole to bipole (or do I?) since they will be set further back behind me. My point is, I am trying to srike a balance in positioning them in a decent position and also keeping in mind that the rears may be replaced sometime down the road. And if that was ever the case, I would want my boxes in a decent position so that if I have forward firing rears, they are placed correctly. As you all know, once the drywall is up, it is too late to change your mind. Could anyone throw me a bone and suggest as to how far back they typically place a rear, especially if you own a pair of LS f/x's?? My room is 22' deep by 12.5' wide by 7.5' ceiling.

Thanks in advance for any replies,