My Sweet Spot is about + - 5 in. on X axis and 3 ft. Y axis. Speakers are Maggie 1.7i s so Y axis SS is much greater. Wife enjoys the sweet spot too, but is usually content sitting to the side out of the range.
For her to best enjoy her favorite songs, my solution is for her to sit in LP and I sit in LP on floor with her legs on my shoulders. What can I say, it works for us. Of course this position wouldnt be best with friends, lol.