Randy, there're a couple reasons for not being so concerned about precise placement that you'd consider suspending one of your subs: first, an examination of the both the null and cancellation diagrams in the article shows that they don't suddenly go from one extreme to the other, but instead follow gradual curves. So, if placement was a little bit away from the point of max null or max cancellation there would still be benefit. Second, your room isn't completely rectangular and the modes in an irregular room have a somewhat different distribution and are a lot more difficult to calculate, as some online sources show. It could be reasoned that placing your back sub farther to the right, more nearly in the middle of the back wall rather than directly opposite the front sub, would more closely coincide with a null in the rear area.
