It fastens with a zip and then poppers on the overlap bit, lots of sealed seams so not really practical to try to alter the front edges.
I plan to do the princess seams all the way down the fronts, just tapering to the shoulder seams to avoid messing with those, and I can unpick the lining easily at the hem.
Taking in the sides would be simplest, but unfortunately won't get rid of the excess across the bust.
I think I'll try using clips for the princess seams to get a rough idea.