^^rsbm
I've not dismissed the idea that BM could have received help disposing of SM's body by an individual who knowing BM, had no reason not to believe he was helping BM dispose of a carcass he poached for its rack. I can see BM concocting a tale in his head about this -- a tale he thought he could sell to Agent Grusing, his trusted acquaintance.
Given BM is most confident when talking about work and hunting especially, I can definitely see BM wanting to get ahead of this if he thought the individual might talk to LE. For example, what if BM asked to borrow their vehicle to deliver the carcass to somebody else?
What if BM did in fact deliver SM's body in a borrowed vehicle to somebody he hired to get rid of her body?
Also, do we know if the Cushman's were in town on May 9-10? Could BM have used a garaged vehicle from the Cushman's?