I decided to implement a little more danger for level 9 and beyond, in the form of a spike trap to kill the player whenever they touch it. The initial thought was to use it to limit the height of the Colossal Jump and force the player to use more control over it, but for level 9 I didn't want to make a ceiling, so I created a version to use on the ground and covered the top of the first building in the cluster with them. It really made the game significantly harder to speedrun, and I'm pretty pleased with the result - and also excited to see how the ceiling spikes influnce the game. Level 9 was a very short section of Nueva Venicia, which made it a great level to test out the spikes.
I quickly finished designing the level and moved on to level 10. I created short sections of tunnel at a time, with a spike-lined ceiling, and tested each section until I was confident it was completable. This process took a very long time, as with the combination of the spike ceiling and the level design requiring use of the tether while standing on a floating crate, this level is incredibly difficult. At one point, I reached a checkpoint, but didn't respawn at that checkpoint, so I went looking through the code to find out why. I couldn't find any issues, but then I realised: this happens when something is colliding with the checkpoint collision box, and this tunnel level is made using subtractive geometry. The collision box was probably colliding with the geometry. I turned off all world collisions on the blueprint for the trigger, and as expected the next time I loaded into the game, I spawned at the checkpoint.