However, just like you, I've had a great deal of experience with placements other than that. Some put them across a long wall, some diagonally. Some are asymmetrical, and in oddly-shaped rooms. Often there are obstructions or disruptions, changes in wall construction or windows. As you might expect, some things are more objectionable than others.

So my best suggestion to you is to keep doing what you're doing. Get a spool of large guage stranded wire and go ahead and try them in each position and see what you like best. This is as important for aesthetics as it is acoustics, and so setting everything up and "living with it" for a few hours or days will help you decide. Probably the most pleasant placement will be self evident.