Oh, also on level 5, I spent ages trying to get down to the box on the pillar without falling below the pillar.
I failed like 10 times, thought it musn't be possible, poked the rest of the level, and then came back before pulling it off.
This could be fixed by adding some sort of debounce to the down action.
Personally, I would be happy with just "you can't hold down to go through multiple platforms - you must press down every time"; but you could apply the same logic with some sort of timer or distance threshold between platforms if you wanted to have your cake and eat it too.
While on mechanics, I would also suggest making "throwing upwards" more forgiving.
I often just dropped the world/crate in midair, instead of throwing it.