The initial sensation is warmth, followed by friction, stretching, pressure and, depending in the length, more stretching, or pressure, depending on which fornix that's pushing. Regardless of his endowment, that's going to rub my clit, based on that angle. This is my favorite position, though the movement of my breasts is sometimes a little uncomfortable. I get additional pleasure from being relaxed and reclined, watching his face and body, placing my fingertips along his lines, palpating each part of him, delighting in the softness of his skin, juxtaposed with the hardness of his muscle, feeling his skin go slick with sweat from his efforts. I get pleasure watching his face and listening to his response as I shift my PC muscle, flexing and dilating deliberately along his length, pushing against whichever direction he's moving his meat at the time. I like that I can grip his shoulders, or loop my arms around them as I get close to climax. I lose my sense of rhythm then, and like to hold on and enjoy the ride, rather than throw off his pacing. I like that I can use my hands to slow his progress, and I am excited to feel the strength in his body as he pushes against my palms and into my body. I like feeling the power in his glutes as I use my feet against them to force him just a little deeper inside. With one of my current partners, I feel friction and pressure to my posterior fornix, and a slight suction and he pulls out just a little to tap-tap-tap me over the edge to glorious orgasm. I feel my mouth go dry as I spill my pleasure onto the bed over and over. I feel the smoothness as I start to perspire, and our waters mingle where our bodies connect, making the activity even more pleasurable, and easier, as we rock together, tummy to tummy. It's fun, as it should be.