I suggest using the two π towers with their backs against a rear wall, spaced 3" - 6" away from it. If they need to be placed near corners, position them a couple feet away from the corners if you can.

If you're interested in making a π cornerhorn, the Alpha 10 makes an excellent driver for a five π model. Make it similarly to seven π cabinets, with the same midhorn, tweeter and crossover. The bass bin should be 4.5ft3 tuned to 30Hz and you can use the same porting as the tower two π cabinet. Put the woofer a little lower than central and place the port between it and the floor. You can confirm this placement with Martin King's spreadsheet to identify standing wave modes, if you wish.