Thanks for chiming in, TLS. My seating position is about 14 ' from the screen and the sub is to the right of the TV, on the floor. After I posted my original question, I had a thought. What if I situated my PC half way between the mic positions and the sub? That would split the distance in two. With your idea of 16' cables, I'd be all set for multiple measurements. The minimum is 5.
As a side note, the S12 sub sounds very good right out of the box, however I figured if it could be optimized, I'd be all set. Also, I'm the only one who listens to the system, so it's not as though I need full room perfection.