In certification flight test the airplane is decelerated 1 kt/second with idle thrust
Worth keeping in mind that, for the formal test programs, the TP folk run a series of deceleration rates so that the book 1 kt/sec (1 mph/sec for even older aircraft) is determined by sums done in the backroom.
No doubt JF will come into the fray at some stage but, in the interim, several of the recent posters know more than quite a bit about this stuff ... so their counsel is worth attending.