I agree with the above - it's the equivalent of asking a human being to live in their bathroom for 23 hours a day.
One guinea pig is usually a sad and lonely guinea pig, no matter how much time you can spare for it!
The dimensions mentioned on sites of the Nero 2 are of the bars and not the usable floor space, either. It is, in my opinion, far too small for one piggy let alone 2. A minimum of 76cm x 91cm is recommended for 1-2 piggies.