Reviving this thread as some new details about the Blackwing were released yesterday:
https://www.roadandtrack.com/new-car...ng-manual-v-8/
I do not know the exact dimensions, but not sure why Cadillac insists on aiming the CT4 at the 2 series/A3 when it appears closer to a 3 series size and the CT5 closer to a 5'er, but I guess they are making their own niche.