Just back from giving it a shot. Notes:
-went out way too hard, need to reel it in and try for a negative split maybe
-couldn't get on top of my breath, potentially just not fit enough
-horrendous stitches
There's still time! Enjoying the process if nothing else
2018 me would offer to help pace you on an attempt but 2020 me would be a few minutes behind you.
Have a go, start at at a comfortably uncomfortable pace and be prepared to suffer... it's only 20 minutes...