This Audi A2 started at Cd 0.288 and got down to Cd 0.204 sealing and blocking,mirror delete,and shallow box-cavity,without any overall lengthening.
Perhaps the Energi will react likewise.And length should help too
Two trim levels of the Mitsubishi Mirage achieve Cd 0.27
Renault Vesta-II got to Cd 0.187 with very skinny tires