Previously there was a small WW in level 5 saving about 8 seconds, but it's very difficult because it is frame perfect. Now I have discovered a way that this WW is not needed, and is very easy to pull off. On top of that, it saves about 18 seconds as oppose to just 8. If you have the low gravity effect on, you can jump from the top of the wall to the right of the spinning scythes by the lever. While there is a kill pane if you try to drop from where the star is, if you jump all the way to the right towards the end portal it does not exist for some strange reason, which is probably just a developer mistake.

Current PB is 11:33 for All Acts but I believe that mid/low 10 is possible.