I just saw this in the Porsche Taycan Group on Facebook. I don't know how they got a hold of this graphic but here is how the Taycan's dimensions compare to the 911 and Panamera.
looks like it will have plenty of backseat space.. also the "foot garages" that the taycan will offer in the back have not been accounted for in that graph
Since there were a lot of comparisons between the Taycan and Panamera, we decided to gather some specs and see how the two 4-door sedans compare to each other. - The Taycan has a wider track than the Panamera - It has a lower height and centre of gravity than the Panamera - Taycan...