I can confirm that Chapter 8: Encore 2 can be soloed in insane co-op mode with strategic use of the dart gun in the top right corner section of the map. After riding the two animal blocks to the left wall shoot a dart at the left wall. Jump on it, then jump in the air and shoot a second dart at the wall, making sure it is high enough so you can jump above the saw blade without hitting it. After reaching the top, you will reach a section where your partner would normally have to throw you to the right. Instead, shoot a dart directly in from of you so it hits the wall directly below the saw blade, and jump on. Now the fun part. Know how you can sometimes land on the corner of a spike block without dying? Yeah. Double jump over the saw blade and try to aim for the left corner of the spike block. It's easier than it sounds and with a bit of practice, it can be done consistently. After landing, shoot a dart at the wall in front of you (the blocks that disappear after hitting the switch) and use it to climb over to the switch. After stepping on it, the animal block will move to the left, then back to the right. AS SOON as the animal block begins to enter the area where the two black blocks were, jump over the saw blade and IMMEADIATELY start hugging the right wall. As long as you hold right, you'll be able to reach the checkpoint without hitting the spikes every time. As this part of the level is the hardest, I recommend doing it first. The rest of the level is relatively easy.