Lay in your bed on your back. Now fold your arms over your abdomen, with your left hand under your right elbow, right hand under left elbow, or some slight variation of that. Now, imagine the hammock just touching both shoulders. Not squeezing, just in contact with. That is, for me, pretty much what it is like in the BMBH. Unless I am using my 25" wide self inflating pad, in which case there is no shoulder contact at all. I am 6'1.5", 210-215 lbs depending on the day.
Now picture just barely turning on your rt. side, just moving an inch or two towards one side. ( your back will be supported by the stiff sides of the BMBH). Now, your rt shoulder is contacting the hammock as it would in all hammocks, but your left shoulder is not contacting at all. So any "perceived" so called squeeze is now non-existent. Same thing of course for an actual full side position.