RE: Deltoid Shape
#1 you would be hard pushed to get your muscle with a flat edge
#2 the delts will never look like the firt one either, they are a flange shape [triangle with curved edges] and the apex is pointing downwards.
#3 SLD is spot on, you cannot shape a muscle, ever. it get bigger [hypertrophy] or smaller [atrophy] it never changes shape.