>>10042321In a study of the breast volume and weight, the breasts on average made up 4.4% of the total fat weight. Sana's tits are obviously an extreme example, so we'll take the most extreme example they found, 12%. Their formula for calculating percentage of the breast made of fat (20%) is odd but lines up pretty closely with the other assumption they make, that 25% of bodyweight is fat weight, so we can just assume they track each other close enough that "breasts are 12% of the body's weight in a titty-monster girl".
Thus one breast is roughly 6% of the total body weight, or roughly one sixteenth. So there's another fifteen Jupiter-Titty masses, a Jupiter-Titty mass is 0.69 Jupiter masses, for a total body weight of just over 11 Jupiter-masses.
This is nowhere close to the threshold for becoming a star (~80 JM). While this IS close to the threshold for becoming a brown dwarf (~13 JM) there is no risk of that either, because a brown dwarf is still roughly the same size as Jupiter, just much more dense, whereas Sana is much bigger.
Calculating the gravitational effects of highly non-spherical astronomical objects is above my paygrade, but I'll try.
Assume the top 15% of her body mass (up at her head and neck) is pulling you in basically in the opposite direction as the bottom 15% of her body mass (down at her feet and calves), those can cancel each other out. We assume the remaining 70% is basically a point mass inside her chest and calculate surface gravity for a theoretical sphere with point mass 7.7 JM and Jupiter radius, I dunno, 2.5 (you'd want to be as close to her nipple as possible to maximise distance and balance gravities). Some assumptions have probably broken down horribly by this point but if not, it'll be something like 27.76m/s2, or ~2.7 Earth gravities.
That's pretty close to the roughly 3gs of centrifugal force that a Gravitron exerts on you, so if you've ever been in one of those carnival rides that spins around and presses you flat against the wall, that might be what it's like on the surface of Sana's titty. with her full body present.
the_man_who_stands_on_sanas_tits.jpg
https://i.kym-cdn.com/photos/images/newsfeed/002/069/825/e91.jpg 
