Nice! I was doing a bit of googling and it turns out getting a big fan to blow through a small hole is tricky. Some interesting reading in the comments of this reddit thread. It looks like picking a fan with a high static pressure rating some quick comparisons accepting you are not going to get the rated cfm of the fan because you are restricting the output (it should be possible to calculate the cfm of each pipe based on the pipe radius and the fans static pressure?), and possibly making some kind of cyclone geometry or something more intelligent in the funnel to reduce backflow of air would be a good starting point.