I'm not using a 40mm fan. I use the standard E3D 30mm fans that come with the hotends.
As for part cooling, I have a blower that sits on the back side of the head block that is ducted underneath the head and directed at the nozzle. It took a few iterations of the blower housing before I settled on the one I'm using, but I'm very happy with the performance of the blower and duct. I've been able to print the Bridge Torture Test (http://www.thingiverse.com/thing:12925) without any sag at all, and my benchy test prints are just about perfect.