Hi there,
Thats definately a nice enclosure in which grandis should thrive (provided the lighting is more intense than it appears in the photo).
I have been keeping and breeding grandis for several years now and they are probably the most enjoyable herps I have ever worked with.
Unfortunately adults of the same sex will not tolerate eachother. You may be able to do 1.2 in a cage of that size, but its very likely that the less-dominant female will be harassed by the other female and will fail to thrive.
1.1 is really the only way to do more than one animal in the same cage (unless the cage is HUGE) and have them be happy.
Let me know if you have any other questions about this species.
- Joe