Position Dock stretched full width without increasing size proportionally
Was hoping to find an alternative solution but I was able to achieve what I wanted by 

defaults write com.apple.dock persistent-apps -array-add '{"tile-type"="spacer-tile";}'


running that command several times (5 times actually) created 5 spaces in the dock which I just placed to one side to make it long enough to fill up the full height.

Now it looks like this