Surround speaker placement height

Hi all, This is the first time I've owned surround speakers, so I'm treading in new waters here. I've read several different things on the proper height of on wall surround speakers. First is, 2 ft above seated position, second is tweeter at ear level while standing, and third is 6-7 ft from the floor. All three positions would put the speaker at different heights.(The WAF would be in the negatives if I put three different holes in the wall.) The 6-7 ft comes from the speaker web site(Polk), the ear level while standing comes from someone who owns the speaker (FXi5), and the 2 ft above is as I understand it, a general consensus when using box speakers on stands as rears. Any more input would be greatly appreciated.