hmm..I didn't really look at the timeline when I answered before. Now I see that the sketch you need to project into comes before the sketch you want to project from, which is prblematic.
Here is a screen cast of fixing that. This is kinda a hacky way to deal with this, but because of the structure of you model it's probably the easiest with out doing a complete redo. the screen cast is a bit rough cuz I was figuring it out as I went-
As an aside, there are a bunch of things you could adjust about your modeling approach that would make things like this easier to deal with, but I guess that's not really the question.