If you're writing erotica, it's always good to know about as many sexual positions as possible, isn't it?
In the Horse of Hector, the woman is on top with the man lying on his back with his knees up and his feet on the bed or ground. She sits on him with her knees on either side of him and leans back against his thighs. This position allows for really deep penetration.
Enjoy! (Umm, your characters, I mean, they should enjoy...oh, you know what I mean!)