I already mentioned it, but MC's breasts in this game is quite technical as it is. It applies several 'formulas' (quite a few, in fact), you can look at them in "PlayerBoobPhysics.cs" which can be found in Hardstuck.dll
'DiameterOfCylinder' is a fun one
Mathf.Sqrt(volume / (3.1415927f * height)) * 2f
So one can play with the formula to see some devastating results (I present * 1f and * 4f results down below).
Problem with Body Customization is it leads to massive problems with clipping. Tits customization is currently broken and I won't recommend to touch the scale if you don't want to permanently mess with a save you have on your PC. Yeah, it breaks scenes where breasts are 'manually animated' instead of applied global physics parameters.