The following modification isn't my idea. There are various Japanese language doll blogs which explain the exact same thing but they're entirely in Japanese. This might be the first English language blog to describe the procedure. At the very least, I hope it's the first.
If you've been frustrated with the range of movement your Dollfie Dream has with her legs, here's a mod for you.
Left: Unmodified DD3 leg/thigh frame
Right: Modified