(FOR BEST USE READ TILL THE END)

There are two sex poses, here is how to use them: (prompts)

Arched upside down is pretty direct and easy: 1girl, UPSIDEARCHED, sex, bent, hetero,1boy,

Twisting spines however is a bit trickier, you may want to discriminate tags or female and tags for male, it gave me best results like this:

1girl, (FEMALE PROMPTS), top-down bottom-up, folded, spread legs, TWISTEDPINES, sex, hetero, vaginal, 1boy, (MALE PROMPTS), standing, spread legs, boy on top,

Do try, post some pics to see how it does!