A player and I wanted to carry a third unconscious creature between both (so we could avoid applying the "Push, drag or lift" rules and move 30 feet as normal). As I have 60 pounds left to carry and my teammate has 135 pounds left, we should be able to carry the third player (who weighs 180 pounds including inventory and himself).
The point of the question is, is this possible? Can we cooperate to "share" the third player's weight and still have a 30 feet movement speed?
Note: Following Standard encumbrance rules (thanks to @slagmoth and @nautarch for remembering me to add this).