Works best with width and height 576x768 but can work okayish in too 728x960 but there will probably be more inpainting to do the bigger you go. The recommended lora might help but your mileage may vary. I added a few variations in v2 so disregard the v1.

For prompt you can try something similar to this but set controlnet to pixel perfect and more important than the prompt (otherwise you'll get limb spaghetti):

(mouth open, singing:0.8), (staring at viewer:1.1), large breasts, mans stomach and legs, naked man laying on floor with his head behind camera, view from mans perspective, man under woman, ridingsexscene, 1girl, 1boy, vaginal, leg down, penis, sex, large breasts, a woman getting fucked by a man, riding a mans cock, woman squatting on top of naked man, man under woman, woman on top, male pov, Professional photo, (full body shot:1.1), RAW Photo, photo of a beautiful woman, best quality, (staring at viewer, detailed eyes), dimly lit, photorealistic, detailed skin, shot on film, analog style, realistic,8k uhd,dslr,soft lighting,high quality,(high detail skin, film grain:1.2),(Fujifilm XT3:1.2),(national geographic:1.2),award winning, hyperrealistic, realism, analog style