Welcome.
I took the advanced course several years ago, learned a few more things than what my wife said she was taught in the BRC. One particular technique they had us do that stands out to me ( since you said you had trouble with the box Uturn )....Just before entering your Uturn, shift your weight to the OUTSIDE of the motorcycles intended direction, butt halfway off the seat, it changes the center of gravity to allow a much tighter turning radius. I learned this tactic dirtbiking in my teens, but it never occured to me to use at low speeds on a streetbike. Since owning a supermoto I use this technique a lot again, and it feels very natural once you get the hang of it. Much like when we used to trail ride bicycles