On what surface do I do the tinfoil exercise? Something squishy like a yoga mat on top of something firm?

Don't worry, it's not your fault I don't know my sit bones' width.

My DH thinks I'm crazy (even though this is my first saddle purchase in a while) and said that if I ride it regularly for 3 weeks and still think it doesn't fit he'll buy me any saddle I want. Ha ha!