I made this simple model to avoid the weird lines that models create when using supports, this test will allow you to choose which top Z distance works better for your models, use the model settings to make the test. I also recommend to use interface pattern GRID and not default, i've got better prints with this kind of pattern.

The top z distances are (mm): 0.15 - 0.16 - 0.18 - 0.20 - 0.22 - 0.24 - 0.25

EDIT Jan 22nd: at the moment it's better to print each part individually, there's a problem printing the whole batch, because it prints everything with the global z height and not those set for the objects. I'm working on it today. 

EDIT Jan 22nd: New feature added (number below), cutted off a small portion of the models, so now it takes around 40 minutes to print (10 minutes improve from V1), solved the problem to print the batch, now all the parts can be printed at the same time, the differences between distances are small, but if you want to change the settings, you can try with other parameters (I will upload a V3 with all the improvements).

The print time it's around 50 minutes (V2: now 40 minutes) for the whole batch with a 0.4 nozzle, USE SUPPORTS, it's absolutely necessary. 

The bottom part of the model it's open, so you can easily analyze the results.