You can place the gyres any way you want them. At the end of the day, only you and your tank will know if the position is right. Every tank is different with different rock work, corals, fish, substrate, shape and so forth. What works for one person may not work for other. The only way to know what works for you is to test different locations until you find something that works for your tank. Sorry there isn't really a straight answer to your question.