An article today from Andrew Benson on BBC Sport, and in there is a chapter asking the question 'Is this really James Allison's car?'
regarding the 2017 Ferrari SF70H.
I think the paragraph quoted below suggests that it is Allison's baby.
The teams knew the fundamentals of the 2017 rules as long ago as the summer of 2015 but the regulations were not finally signed off until early March 2016. At the very least, the fundamental concept of this year's Ferrari - its wheelbase, dimensions, basic aerodynamic philosophy and so on - was done on Allison's watch.