I'm no head shrinking expert. I'm not trying to get others experimenting on head shrinking. I don't like giving advices regarding head shrinking because I don't want to be blamed if it didn't turn out as planned. I have gotten less desireable results like these heads that ended up smaller than the "normal" sized head. By "normal", I mean the collector sized heads.
The final size of the head shrinking process is usually reached after about two weeks. I normally repaint the dolls a few days after the shrinking. I like how the faces of the shrunken face turned out so I decided to keep them. I used to discard over shrunken heads since they looked like they don't fit in my collection.
It is best to place the head on the body immediately after rinsing off the acetone or before it completely hardens. Head swapping these shrunken heads is a literal pain. The shrunken heads become hard since the plasticizers have been removed. I had my fingers scalded because the head should be really hot for it to be removed. The Grace doll has no knee nor ankle joint but I want her to have one so I may still eventually head swap. Good luck with that.