I think I must have got lucky with this one - completed after 2 tries. I tried the obvious way and was 2 short, so on the next attempt I thought I'd try something completely different and it worked. A nice level though - I can see why people would struggle with it.
Now that was sly.
It took me over 30 attempts to complete.
All of a sudden, after staring at the screen for a few minutes, it just jumped out and hit me.