This myth is slow to die, despite all the information that we have to the contrary. Grip width has no real bearing on hamstring development. Again, for best results, keep your heels up also. Also, have your spotter stand by your feet so that he can give you feedback on your hip elevation. Commonly, the spotter will stand behind the lifter's head where he can't even see the hips, and consequently, serves no purpose at all.
Many trainees prefer the dumbbell bench for working the hams.
I advise against this exercise, however, as most find it difficult to raise the hips when working with dumbbells due to balance problems. Also, the increased range of motion seems to throw added stress to the chest and shoulders, making this exercise less effective as compared to the barbell bench. I must also caution against the decline bench press. The angle of the bench in this case prevents you from raising your hips using your own muscular force, making it a rather useless exercise. Just a few of the items I have found to be most effective in creating the Bogen physique.