I was pretty sure it couldn't go down lower since when I first put it in a few years ago it went down until it clunked against the bottom - or whatever was stopping it. Been busy but I finally got around to seeing if it could go further down and I can confirm it cannot.
Could this be because the bike was originally designed to have stem mounted shifters, so they made it so the stem stuck out more so there was a place to mount the shifters?