Ok I found my old cubby and compared it to the satnav cubby.... I think a 7" screen of some sort would fit, but you would have to butcher the cubby up so much and you would also loose the lid so personally I would get a satnav one
You would have to cut all the back off from the inset bit...
Which is where the lid is attached to
Your only real option with the standard cubby is to fit a smaller nav or tablet inside it, a 5" one maybe...