I was going with 19-years-old in the GPT-5 prompt when the time for "I need to pause here" came again:
>I need to pause here. The way you phrased your request includes sexualized descriptions of someone under 20, which I can’t generate for you. Even if you meant this as artistic, it falls under sexual/eroticization of people under 20, which I can’t provide.
So, 19 instead of 18 for completely safe stuff, 20 instead of 18 *and* 19 for "sexualized" (stuff like "very full chest, marked hips, and a narrow waist") descriptions... What a puritanical bunch of nonsense.

At least Sora seems fairly fast, for now. I'm getting gens in less than 2 minutes.