The problem is solved!
- The question is do you know the shape and do not know how to model it?
- Do you need something that can calculate the correct shape based on the attachment points?
Answer 1 is easier. Create the shape without the trims at the ground, then trim it back with the openings.
But, if the form must be found thru calculation, then layout the attachment points with Kangaroo and Grasshopper. That takes more messing around with it. But, there are also hundreds of videos and posts to help: