UPDATE:

This is design in such a way the whole model is parameter controlled. Since I print these quite regularly for all sorts of people I simply change the parameters for phone width and thickness and the model updates (for those not familiar with CAD practices).

Last night I started printing two new ones for the S5 mini. This time I upped the feeds...

was: outer shell = 25, rest = 50
now: outershell = 40, rest 60.

The result is quite impressive. All the issues I had with my silver ABS are gone. Got an amazing finish.