None of the example images were post processed or scaled.

Trained with the following resolutions...
448, 512, 576, 640, 704, 768, 832, 896, 960, 1024, 1088, 1152, 1216, 1280, 1344

Chroma seems to know what Jack O Challenge is but I had a hard time getting clean results so curated some Illustrious images to create a LoRA to help it along.

I used a number of trigger terms in the caption, as well as natural language, but they don't seem to have any noticeable impact, the LoRA just works if enabled.

A weight of 0.6 was a good balance between floating body parts and "too real" (which seems to introduce quality issues).

Initial terms I used ...

jack challenge
jack-'o_challenge
jack 'o' challenge
facing away
side view

One of the prompts I used, for the gym, which I think worked better than the beach scene, is shown below...

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aesthetic 11, realistic air brush style.

This is a mature, adult woman with a large, oversized chest, her meaty assets spilling out of the tube top and resting on the ground.

She's doing a bent over pose with her rear up high, which results in her standing with her legs spread wide, straight legged, bent over to rest her chin on the floor, facing the viewer.

Pale skin, pink glossy, swollen lips, long double braids, long fake eyelashes, large lavender colored hoop earrings.

She's wearing white high-top platform sneakers and long white sports socks, both with the black playboy bunny logo, pure white bikini.

It's overcast and a cruise ship can be seen, clearly in the distance on the water seen through the window.

Sharpen the image to include the essence of the twill fabric of the bikini and knit material of the socks.

She's in a gym where there's weights, machines and a few men staring at her, mostly bokeh background.

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I like the way it has influence from Illustrious, at least those refined models that give a cartoony 3d look, and this represents it pretty well but there's something missing and I'm continuing to test parameters to get a better likeness. Ultimately I want to make a character LoRA containing those that I like the most from the e621 set. I've already started work on that.

I don't like that the hands are sometimes scrambled and often blurry, but it works well sometimes.

The limbs seem to be weirdly proportioned but I'd expect that, I guess, in a pose and style that's as unreal as this unrealistic pose is.