Merging Surfaces? For diagrid script

Hi!

I am trying to create a single surface from these two surfaces (as shown in picture). I cannot merge them as to create the shape I trimmed one of the surface edges. Is there a way to re create that form as one surface? or another way to merge them that will work? This surface is to be plugged into a grasshopper diagrid script.

Attached are both the Rhino file and the Grasshopper script. I am a novice with these softwares so apologies if I have missed something obvious.

Cheers!

DIAGRID ALGORITHM.gh (10.7 KB)
Roof experiment.3dm (7.9 MB)