Well... I thought and thought about it and figured out a way to get all three of them in the trailer. I took a bolster out from one of the dinette benches making it wider and figured RD could sleep there. Then I brought in a stiff foam mat from one of the crates and made a bed under the table. That was a nice hide hole for Bridget the smallest. Then Lee Roy the Mystery dog could sleep on a rug by the door. The cold was so bad I think my muscles were sorta in spasm from shivering and kicked off a bit of a migraine. So I took my cocktail of meds and went to sleep (i.e., dropped in to a drug-induced coma). When I woke up in the morning, the three dogs had totally re-arranged themselves. RD under the table, LeeRoy on the bench and Bridget on the rug by the door.
Go figure.