I did the 'butt-o-meter' thing at my LBS but I didn't buy it. It said that my sit bones and my husbands sit bones were the same distance apart.

I came home and tried measuring them myself. I sat on the floor and grabbed a fabric tape measure. I held it between my fore fingers and thumb with about 5 inches between my hands. I rolled onto my back, flipped my legs up over my head (ie. held them up in the air towards my head), and then felt around on my butt until I found the bones on both sides. I positioned the tape measure at the bones and held on to it. I put my legs through my arms still holding on to the tape measure and voila! I had the distance between my sitbones.

(I was not nearly as contorted as this description makes it sound. )

Sure enough, DH and I do have the same width between our sitbones. Who would have thunk it...me with my big butt and him with his 'no butt'!