This is a beautiful bra. I would personally feel more comfortable going up a cup size, due to the plunge style. I feel like I'm spilling out the front a little. Or maybe the style just isn't that practical for a G cup.
Similarly, the two thin shoulder straps, while pretty, aren't ideal for very large breasts. I'm more comfortable with thicker straps. I'll still wear it, but likely just for short periods with certain outfits.
