Any limit as to RV length on the Alaska Ferry

I would strongly agree with driving to Prince Rupert and starting from there. Play around with the starting date. We did and got "civilized" departure and arrival times. We needed a room only one night (on the Ketchikan to Sitka leg). The other legs were in the daylight hours.

Also, we met a couple in Whitehorse who left their big 5th wheel in Texas and, for this trip, bought a Lance camper for their Dodge diesel (like our setup). They were having a ball with their newly discovered agility!