Its too tight at waist and back panel been cut away

Helped my friend to upcycle this dress.  Its pretty and the drawbacks are too tight for her on waist, too long, and there is a hole at back panel near hem.  From picture above, its too tight for my dummy, cannot close the buttons.

Don’t have a torn garment with similar fabric to go with it and so I use deadstock fabric  to replace the back panel.  

I detach the back panel and put onto dummy again, the front panel is too small, have to add at least 4 inches at back and so I decided to do a replacement back panel from below shoulder yoke all the way down to dress hem.  By doing this, waist line at back is free up and my friend will not feel tight.  

Here you go.  Now the back waist is released, even for the size 10 dummy can button up this size 4 dress now.  I didn’t put the belt loops back as wearer can now choose either with or without the belt on.