I did some experiments on body measures affecting answers for Koikatsu body related questions in school mode. Here are some of my findings.

------Question about height preference------

This one is simple. Only affected by height.
high <- 61 | 60 <-normal-> 25 | 24 <- short

------Question about fat/slim preference------

Not affected by body texture type and some other adjacent numbers. Only affected by these numbers:
A. lower upper-body width
B. upper lower-body width
C. Lower upper-body depth
(other depth numbers all have no effect, just this one)

A+B+C=X, and X is the key number here.
Fat <- 196 | 195 <-normal-> 105 | 104 <- slim

One thing I need to mention is that during my experiments, it seems to me that B possibly have a slightly bigger value in the equation than A and C, but it's not too far off. Basically 195 and 105 are the point of determination but there could be a +1/-1 margin.

------Question about breast size preference------

Basically, only affected by breast size.
Upper upper-body depth, neck collarbone depth, breast pointiness, all have no effect.

However, This one is a little more complicated. Because there's this great thing called bra push-up mod to be considered.

When naked/push-up mod off
Big <- 71 | 70 <-normal-> 40 | 39 <- flat

when push-up mod on and wearing student uniform plus normal bra
Big <- 76 | 75 <-normal-> 43 | 42 <- flat

You can see the difference gets bigger when the numbers go up. It's not just a simple x-5=y or x-3=y all the way.

Also, different bras have different effects.
On top of that, different top outfits also have effect on the answers.

For example, say here is a girl with breast size at 75 and wears no bra.
She sees herself having big breasts when in gym cloth,
but she sees herself having normal breasts when in archery cloth.
Same girl, no bra, push-up mod on, different outcomes in different top outfits.

It gets a little too crazy for me to keep testing after this finding. I think I'll just use the naked numbers and uniform with bra numbers as basis when trying to get a certain result. =D

Just thought about a way to make things much much simpler for the breast question. Press k to switch off the push-up mod before giving your answer to her. This way you can use the 71/70~40/39~ set of numbers and don't have to worry about anything else.

(I've tried it. It works. A girl with a 49 breast considers herself flat in full-body swimsuit with push-up mod on. The next time she asked that question I switched off the push-up mod before answering, she considered herself having a normal-sized breasts this time.)

@Pulptenx Thanks for clearing up the factors for the Chubby/Slim requirements. I have some girls that anyone would quickly declare EXTRA THICC but they considered themselves thin and I also have girls that are thin as rails but considered themselves chubby... I was so confused! Thanks for your observations.

Glad to be helpful. I play the game in Japanese so the terms I use here could be different. I hope they didn't cause too much confusion.

Since this place seems to be going to shit, anyone who wants to share this info on other discussion boards, you are welcome to do so. I claim no ownership to any of it. =)

@Sibushang
Just found that lower upper-body depth is also a factor in the fat/slim equation. I've edited the post. Still not 100% sure but if I were 70% sure before, this time I'm about 96% sure now. =D