12cm/120mm fan shroud (for DIY swamp cooler)

Made this 12CM fan shroud to increase efficiency (in silly, uneducated theory) and at the very least, to help locate-to-center the wet/soaking media tower in my DIY 5-gallon-bucket swamp cooler. I have no idea whether it increases effectiveness of the evaporative cooler due to aerodynamics, since A. I don't know squat about aerodynamics and B. I haven't bothered to do any A/B testing. But it definitely helps keep the cooling tower properly located within the bucket and centered under the fan, so