For some reason I had a bit of difficulty printing this, but I did have the best luck at lower layer heights (I used .1) with the top facing down. I put support blockers on the threaded nozzle holes, but left the supports for the mounting posts. With supports on everywhere I was having trouble separating the supports around the holes and having it still look good, but without supports the holes weren't printing well until I dried my filament and lowered my layer height. Also, the supports for the posts end up being very tall and skinny and fall over easily. Do what you can to make sure your adhesion is good. Feel free to experiment.
The threads on this nozzle rack actually turned out quite nicely, and I was able to thread the nozzles in to most of the holes perfectly. There were a couple that weren't quite perfect. Use a tap and/or adjust your printer calibration if you have trouble.