This particular problem is driving me nuts. Although I managed to fudge it on my second model, I didn’t have as much surface area to work with on that one. This one is huge (680 m long) and as you can see it goes in various directions. What I need to do is add a radius to all the highlighted sections.
Fredo6’s FredoCorner would do that for you. But I have no idea if it works with what you are currently displaying as your operating system and version of SketchUp. It’s free from SketchUcation, but you have to sign up.
@Mim86 SketchUp Make 2014 should still install and run on Win XP.
It uses Ruby 2.0.0 which may be required to run many of the extensions these days.
(FYI, SU2013 and older runs Ruby 1.8.6.)