The reason why I did that in two surfaces was because it was done also in that tutorial. The guy explained, that for one surface it is too much so it’s better to divide it in two. I had also to cut the surfaces from bottom. So it doesn’t need to twist so much.
I did also another presentation for you.
here is an alternative solution. trying to create sections like the tutorial can become tedious. lots of experimenting.
here i just deleted the blends that you had, used freeform blend(set flow for the small side to default and the corner area to connect), and adjusted the shape with the slider, then patched the small surface with a square.
mirror the halves and used freeform blend again. i made sure that the flow settings were set to "Edge Align"
viola. 6 mins later... good enough for all practical purposes.
you may notice that there are 3 areas that do not create the Green C(i am using tighter tolerances than you used as well) but this seriously does not matter. the blend in the corner only needed a few manual tweeks of the CVs to make it Green. i was only moving them .001mm at a time. that is not a noticeable amount.
sure you could build this lighter, but this took no time, highlights nice, full history and stitches fine for production.