Am working on creating an urban downtown area, and running into a problem with the flattening polygon in FSX. I have UTX-FSX and FSGenesis-FSX installed with mesh at 5 metre resolution. Trying to create a flatten (using FSX-KML) with detailed resolution results in a sharp edge and cliffs where the flatten polygon meets the surrounding terrain, which varies considerably in height throughout it's area. Wondering if there may be a way to make the edges extend outward more gradually, e.g., at a shallower angle, to help smooth everything in more naturally.

Thank you for the suggestion. I upgraded Airport Design Editor to version 1.26 and allowing points on a flatten polygon to be independently edited, which is helping overcome the problem.