I built this theme as a child theme from Boardwalk as I wanted them to share a similar design and patterns.
Having said that, there is one major difference: the layout of the blog page.
In the end, I decided to start from scratch with a fresh download of Underscores and only copied what I would actually reuse.
What I learnt from this experience is that if your child theme is going to profoundly overwrite its parent, fork it. This will allow your theme to be more future-proof.