OK, the picture makes it clear what has happened, I had a similar experience, I think you are on the right track gluing bits of wood in, here is a picture of such a repair,
If you glue in as many pieces as you can, you can keep filler to a minimum, then if you re route using a template and just skim the surface with multiple shaving passes as opposed to digging in, it should come out fine.
I really can't tell what's going on on your photo, Muzz.
Seems that you've done a great job repairing whatever problem there was.
I just made a diagram and basically this is what happened to my cutout:
I intend to glue the sawn off piece back to the body and do a second cutout.