Going back to the first muslin here is the photo showing the length issue in the bodice.
To make the adjustment I measured the additional length needed (1.75in at the full bust + 1in at the centre front).
Then I cut a line from beneath the underarm bust dart to the full bust point then vertically down (avoiding the under-bust darts). I left a hinge at the side seam stitching line so the side seam length remained unchanged, then pivoted the bottom piece down 1.75in.
This seems to have added the right amount although I had to play with the dart position and length a fair bit in the muslin form because the angle had pivoted down. I think now though, the problem is solved.
Here is the first muslin: