With PLA as my plastic of choice, I found that objects with short layer times benefitted greatly from a fan directly at the extruder. Greg Frost's Lm8uu X Carriage with Fan Mount fulfilled this requirement for most parts. However when printing thin layers with short layer times I found the side opposite the fan could still come out messy. To remedy this I added a fan to the other side.
Made to mount a 40mm fan on either side with m3 screws and nuts.
This does increase the width of the X carriage by about 18mm if using a 10mm thick fan. I was able to move my build platform over to compensate without losing any build volume.