[Carl n Susan]

I have taken most of the ferries in that area. I usually take the car or walk on. I haven't taken the 5th wheel on any yet. However I see commercial tractor/trailer combos on the most of them.

The Canadian ferry system seems to accept long vehicles on all their ferries. The Vancouver - Nanaimo (Tsawwassen-Duke Point) route is no exception. So you should be fine. I assume you are aware that route is one of the most expensive for RVs.