Well well well.
I've just found an out of bounds clip in
5-1 In the first glider section two grass blades cross each other left-up from the glider. Run into the grass blades that stretch along the entire gliding section from a point of view where you can't see the blades due to the perspective. Jump into them and you will float. You know what to do now right? Well infinite scaling is way easier if you jump back and forth. After some time just fly over the wooden fences on the bottom. If you are high enough you can fly a really long time into other sections.
Every world has an out of bounds clip...