Here's an interesting comparison between the new and old cars:
http://www.planet-9.com/news-items/82702-tale-tape-does-981-measure-up-987-a.html
The increased rear boot depth, and the reduced height above the engine deck in particular, confirm my intial impressions when I viewed the new car at the launch. The poster makes the point that the increased deck height above the engine could be to create space to allow Porsche to install a taller engine and suggests, perhaps, a turbo-4 or even a GT3 flat-6 with a taller intake system. Who knows, but food for thought anyway.!
Jeff