If you don't want to redownload the updated Aiko Short the chest yScale is what you need to change

Chest was yScale 120% rescale it to yScale 110%

leave abdomen at yScale 120%

This is how to make Aikos Clothes Fit better
This is what was added to the readme

Load Aiko, it doesn't matter if you apply the clothes before or after you apply the Aiko Short pose, but make sure to follow the instructions below

For Clothing Figures (Aiko CLothes Only)

Load each clothing figure
On each clothing figure go to Object menu and
select Change Parent
Choose the (Aiko Short) Figure and select "body"
the check Inherit Bends Of Parent
then click OK

Then conform each clothing figure to the (Aiko Short)Figure

On each piece of clothing from the abdomen up select it and make sure you have the "body" selected.
Then go to the yScale on the Parameter Dials and set it to 110%

Do nothing for any clothes from the hip down

The yScale on each piece of clothing from the abdomen up (remember have the "body" of the clothing selected) is set to 110%.
If the clothing figure is a full dress select still just select the "body" of the dress.
Then Conform each piece to the (Aiko Short) Figure.

Then pose the figure as you like (you may have to make small adjustments, but not to many I

hope)