Best sub position for my room?

I plan on getting two tower speakers or bookshelf speaker on stands for my HT. My setup is as follows. Room is 12 ft wide with a 9 ft across screen. That leaves me about 15 inch clearance on either side of screen for L/R. Because the L/R will be in either corner of room, I will now need to move my sub, which was in the right corner about 1 foot from right wall (facing screen). Given that the front right will now be where the sub is, what is the best spot to move the sub?


Also the right wall is an exterior wall (drywall on brick) and left wall is framed double-drywall... if that helps.