shoulder carriers:
fine as long as you keep your side neck muscles flexible (the side u carry your bag on), balance yourself as much as possible by weighting the other side of you (any additional accumulations, perhaps a big H bag with a new birkin in it??!!!)
hand/elbow crook carriers:
same
hint: it seems shoulder carriers have a tendency to raise up the shoulder a bit, which can lead to spasms.
I make it a practice to consciously press my shoulder down. helps me...great practice for WHEN i acquire my first Birkin. !
angie