I have tried using the regular and the CB++ bodyslide - and they have no effect on my character in Skyrim - it seems whatever body type I selected when installing the CBBE body is the one that stays. (and I selected custom)
I have located the meshes in meshes/actor/character/character assets - then took the new nifs the bodyslide created and manually put them there, but to no avail. But I know these meshes are doing something, because if I remove them, my character has the default body with underwear - so why do the meshes not affect my character's appearance?
In addition, the breasts bounce just fine when wearing clothes, but not when nude.