Well here's another one it might have been said b4 but didnt want to read every post....put a couple pillows under her butt to angle her g spot at more acheivable angle. Gently put pressure just above her pubic bone to futher expose her g spot for stimulation. Penetrate slowly and not all the way, just tease the g spot, also tell her a nasty story!! Get in her mind and dont be afraid to use your hands all over her non sexual parts as well. The more comfortable she feels with her body, your chemistry, etc the more proned she will be to let go. Dont be afraid of toys in this position either, a little vibration on the clit can go a long way to push her over the edge. Cant strss enough about the mind enough though. The position is only an easier way to hit her spot not a full proof plan...
Good luck and happy intercourse!!!! lol