Does the girth of the penis stimulate the g-spot or does it just stimulate the clitoris and vestibular bulbs?
Not to be overly technical, but the clit (head), vestibular bulb, and G-spot are all part of the clitoris (clitoral complex). The head of the clitoris is outside the vagina, so the penis would need to be angled correctly to stimulate the clitoral head (girth would not matter too much). Girth could help stimulate the g-spot, but for best g-spot stimulation the angle of penetration would be of more importance. Of course, I'm speaking of stimulation attempting to achieve female orgasm (all female orgasms are clitoral in nature and the majority of women cannot orgasm from penetration alone). Larger girth would generally generate a more pleasurable feeling, but not necessarily be orgasmic.