I would probably go with something along the lines of:

Dependent claim 5 relates to features which are purely a matter of routine. "Purely a matter of mechanical skill" is another possibility.

The sense is that these features can be carried out in a routine or mechanical manner by the person skilled in the art, i.e. nothing new or inventive is required. I can't find an example of this exact usage, but here are a variety of references which you can piece together.

This was not simply a matter of routine as this area of research was quite unexplored at the priority date of the patent in suit. (p. 15 of 17)
http://legal.european-patent-office.org/dg3/pdf/t961112eu1.p...

The mode of connecting motor 60 to the frame is purely a matter of mechanical skill (about 2/3 of the way down)
http://www.wikipatents.com/gb/1487471.html

The arrangement of stops is simply a matter of mechanical skill, and there could be no invention except in the precise form employed. (about ½ way down)
http://bulk.resource.org/courts.gov/c/F1/0243/001/00000890.t...

Adjustment of such variables is simply a matter of routine by one skilled in the art. (just over half way down)
http://www.wikipatents.com/gb/1199376.html

Dictionary entries from Klaften/Wittman/Klos Dictionary of Patent Terms

inventions of such a kind arise usually from mechanical routine - derartige Erfindungen pflegen sich aus der mechanischen Tagesarbeit zu ergeben, sind nur “handwerksmäßige Maßnahmen”

handwerkliches Können - mechanical skill

routine - mechanische Tätigkeit, tägliche Beschäftigung