I'm telling you guys, I was using a mere 50 lb. dumbbell, for the Unilateral Dumbbell Floor Press, and it was almost as difficult as doing one-armed pushups.
Rooting your elbow into your side, and doing reps from a dead stop, make this exercise doubly challenging.
But unlike doing one-armed pushups, this movement left me with no residual, next-day shoulder pain. And I suspect it will lead to some hypertrophy as well, particularly upper pecs.