Here is the photo showing the shoulder belt in relation to the seat as it was placed when I took the pictures yesterday. It was indeed forward of the seat, pulling the front of the vest forward, creating the gap.
Today, I moved the seat up and also moved the seat to a more upright position. These are the results:
What do you think? Is the fit ok? There is still a bit of a gap, but the gap is above her armpits, across the actual chest it is still tight.
Now that I have given this more thought, I won't be using the RSTV as much as I originally planned, there are more places I can the Radian along. However, there are a few times we'll definately need it, and I'm feeling better about the fit after moving the seat today.