I also went in and ended the 3-wide after the first corner onto D938 (this corner does not really have a name but I've borrowed the name of the road it turns onto). This required some changes to the next corner and the hairpin.
Here's iteration 2.
After a couple more text laps with more cars, I've decided that there are some places I want to widen the track in order to make passing easier in certain places. I may also shorten or remove some lines from some corners.
Well, progress is being made. I'll update again after more testing.