Powering LED strips with 5v power supply - safety question
I think the way you want to do the connections certainly makes sense. It is as I would to them as well.

And as you said, for safety reasons and to fulfill the requirement of the manual, you should connect the V- wire to the protective earth (FG) terminal. The point is, if something goes wrong and there is current flowing out of the V- terminal, it will find a low impedance route to the earth through this connection and the earth wire coming from your home's electrical installation and not through the person that potentially comes in contact with the circuit. 

That is also the reason, why you should hook up the chassis of both the power supply and the encasement to the earth. However, I make the educated guess that the chassis of the power supply already makes contact with the FG terminal (you could easily check this out with a multimeter) and so no special care should be taken there. The connection of the chassis of your encasement to the earth could be done either with an extra wire or with the mounting screws/holes -if any- that you will use to mount the power supply, or with both ways.

All these of course under the condition that the PE terminal of your house's installation is indeed wired to earth.

One last point: If you indeed indeed to hang the whole thing from the ceiling, pay attention that this method of mounting is NOT recommended, as you can see in Chapter 5 of the manual you have linked. The reason is, as they say, that in this case the heat from the electronics will be trapped and not be able to leave the enclosure. That would mean probably that the output power will be reduced and/or the power supply could shut-down due to high temperatures or worse be damaged. And you are anyway quite at the limit if you see the derating curves, so I wouldn't do it like you intend to.

Lastly, I assume you have already considered this, but it is also imperative that your enclosure has air vent holes.