The mobile navigation is a great concept but you are using up valuable screen real estate for 4 links that stay pinned at the bottom. That might not seem like an issue depending on how you are viewing it but for smaller screens like some of the smaller apple phones screen real estate is important.
Instead of pinning 4 big buttons at the bottom just add them to your mobile footer which already displays at the bottom of every page and it scrolls with the page. If you want to differentiate those 4 links then you can increase the size or colour of the links to differentiate them from the rest.
I had the same addon active for a day and opted against it once I looked at the screen on a smaller display size.
Look at the bottom of DN.ca on mobile (or desktop) to see how I incorporated the links I wanted to highlight there.