I used to sleep with all three of my dogs, in a queen sized water bed:
Joe, yellow Lab 95 pounds
Blackie, Lab/Beagle 55 pounds
Gus, Pit/Golden/?? 75 pounds.
Gus and Joe would sleep butt to butt and lie up against me, and it was very comfortable. Blackie did some weird thing where she would hang her head over the end of the bed to the point her nose was about 4-6" from the floor, so she didn't take up much room. Later on, when Gus was an only dog, he would put his head on my shoulder and I would wake up with a dead arm quite often.
These days King sleeps with me a lot, he's like sleeping with a corpse, he hardly ever moves. Molly walks around a lot and seems to get hot, so King (And I thank him for doing it, I get guilty when I do it) finally just decided she had to go. She sleeps on the couch most of the time, but once in a while she will spend a couple of hours in the bed with us, but eventually, she moves around or does the spin once too often and King stares her off the bed. My GF came over recently and I had both of my dogs, along with her dog, "Heather", one of the bigger female Labs I've seen in a long time, all piled up together. It was ok for a while, but eventually Molly started panting, and King and Heather stared at her and off she went, to the food and then to the couch, where she could spread out a lot better anyway. King and Heather (Not the right name for her, IMO) seem to both be really compatible, sleep wise, they both sleep a lot, and sleep very deeply. Last time she was over, I woke up with both Heather and King in the middle of dreams. Heather was in between me and my GF, and King was on my right, barely on the bed, and they were both hitting me on the face with their front legs. I let them finish up and them moved around enough to make them get up and reset themselves. They were both back to sleep in a couple minutes, it took me about an hour. I wish I could sleep like they do.