This is a really good question. I have trouble believing that the ramps would always be Vette friendly. And then there's how tight the cars are packed in. I asked One True Chevy Girl about this a couple of years ago. Since she lives on Vancouver Island. This is what she told me.
"So, just in case your exit plan may include Vancouver Island, honestly the ferries are not scary. I understand all your concerns with the Vette! The trick on the ferry is to pick one of the less crowded (off peak) sailings times if possible and ask to be put on the lower truck deck. It's where they put the big rigs, RVs, tour buses and so the lanes are much wider - usually double wide which gives loads of space around your car and for doors to be opened. We take turns staying with the vehicle (it's only 1 hr/20min over). Noisy yes - but worth it for peace of mind. In the 30+ years we've lived here, we've never had any damage to any vehicles whatsoever. The on/off ramps on the large ferries (ie: from VanIsld to Vancouver) are so highly adjustable, they're no problem for the Vettes. The Corvette Western Canada Conference was held in Victoria this year and the 25ish cars (C5's - C7's) that came over had no issues whatsoever. We also have Deuce Days here every 3 years - where hundreds of Deuce Coupes take over the town. They come on the Washington to Victoria ferry and many of them are SUPER low. Also, I didn't hear any mention of anybody having problems - and as you can imagine, complaints travel the fastest around a group of car peeps!
My only ferry concern would be on one of the small Gulf Island boats - like Saltspring. They pack em on like sardines while backpackers, kayakers, tree-huggers, dog walkers all maneuver through the cars bashing mirrors to get to the front of the boat. I've seen it happen."
So there you have it. Being a prairie dweller, I have limited experience on ferries. Don't know how you get a spot on the truck deck. If I was planning a trip out there I would ask Franci how that is done. Really enjoyed the times we went across on the Harleys. Motorcycles are first on and first off. It's great. We rode by over a 1/4 mile of cars and sat at the front of the line. I assume it's the same move for a car with a reservation.
Bic