Yup, it is safe... However, the grids now come in two sizes in the same box, so your allocation of grids will have to be well planned.
See this thread for an explanation of the grid differences: Warning about new NIC panels
The boxes are mixed half & half, so use the larger grids for roof and upper areas of the sides (above easy bunny reach)
I have a 2 lb little gal, and she can barely stick her nose through the grid.
Mind you, I've found that the rubbermaid grids that I bought at Walmart only had the smaller grids, so it may be a brand-specific thing.