Yeah, just take the length of the room, and divide it by (1+√5)/2, and place a new wall to make that the width. Then, if you feel like it, take the width of the room, and place the ceiling at the same ratio.

Then no surfaces will have harmonics of each other.

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs
-Chris