It's difficult to envision precisely what your design requires. Would it be practical for you to sketch out a simple drawing and add to the post? Even a pencil sketch photographed by a cell phone is better than counting one someone else's imagination!

Cylinders are circular in cross section and have no opposite corners. If viewed from the long axis, it is a rectangular cross section, which would have opposite corners, but then the axial positioning of the cut-outs become slightly vague.