Maybe a hint? You access the room from the bottom. Although I can think of a way to go from the bottom left, its near impossible and from the bottom is not that hard once you get to understand how.
The room with the O, there's a powerup that will make you fly. The game allows you to queue a powerup (carry one while you grab another one).
What you basically need to do is fall down. Grab the powerup and wait with activating it until you nearly can't. Then activate it and wait at the bottom for the new powerup to spawn. Grab it and fly up as high as you can. When your powerup stops, immediately activate the queued one and you should be able to reach room 43:13.