So if you use E3D (or clone of it) V6 and 40mm fan and PetsFang designs - more often than not you face issue with under-cooling because of how air flows (leading to occasional need to do cold pull and all that jazz) .
Most efficient way to cool it is by pulling air rather than pushing. However good efficient fan (i use 40x40x20 to make it real) will create wicked air stream across bed that might lead to issues when parts cooling unevenly, if you printing multiple things or just large thing.
So here is shroud for 40mm fan that will push air away from bed. Hoozah