I've had my C-Max Energi PHEV on several BC Ferries with no issues. It has lower clearance than the Kona EV I think from looking at them side by side. I have never been sent to a special ramp upper or lower traveling to Duke Point, Victoria, Galiano, Salt Spring etc. No comments at all from Ferry personnel.
Edit: C-Max Energi clearance is 5.5 inches. Kona EV is 6.2. So all seems okay.