Hey Frenchy,
Here's a short video using a couple scripts:
I used points to mark the start of the openings so I knew where to blend. It could help if there were "many openings", but at the same time, selecting that boundry would be tedious, if there were many of the little openings. Not sure of any way to automate that. I would guess there really isnt any need for the boundry to be "Not a square", so I would just use the rectangle tool and go from corner to corner on the surface and use that to trim. Just running the "untrim the outer edges" script only.
