I've got to add to this....
I've found plain old push Ups several times per week seem to keep things stable also, I think the shoulder problem comes from having your shoulder girdle restricted as the barbell ir dbell forces you into the bench..
So days off the gym I'll do 5 sets of press Ups, I don't kill my self either , 30 odd reps a set, somtimes less, I usualy do 5 sets of crunches too