Thank you , this is a good solution.

> I've opened up that little bit of space in between the flaps by copying edge lines and using Edit > Trim and also cutting out the margin in the corners as well.

The way I've did it is by drawing a rectangle and sliding it along the corners to make a cut using bool diff. I am not sure I understand why you would copy edges and trim them. Wouldn't that be a more complicated way of doing it? Did you create a rectangle from the copied edges or something else?