I 3d printed fan shrouds which relocate (move forward) the front fans all the way so its nearly touching the drive trays, it dropped my drive temps by about 5c. A massive and unexpected improvement for such a simple mod. I use the phanteks T30 120x30mm fans with high static pressure, so by putting them right up next to the tray, im better able to utilize the capabilities of the fans.
I use 4x 120mm fans at the front and the shroud can be fit to the top 3 fans, the bottom fan obviously not because of the drive cage at the bottom. Can post the STL file here if anybody wants.