First of all, thank you for appreciating my work.
As far as I'm concerned, the opening/closing walls are passable with a certain amount of practice and attention. You certainly need to have mastered flying, and the best thing to do is to position yourself exactly in the center of the passage. However, there's a method that makes the passage quite easy, the same method you can use in the original game. I thought everyone who'd played the original version would know this "trick," but apparently not. I don't want to spoil the fun of figuring it out for yourself; perhaps you might find it by watching some gameplay of the original game on YouTube. Otherwise, if you really can't figure it out, I can explain it to you directly.