The Saturn Ion Quad Coupe used to have a nifty demo video of how easy it was to put your kayak into the car, so I did a bit of double-checking. Sure enough, here's a review from someone who says that his double bass fits just fine (though this wouldn't allow a front-seat passenger): http://www.carsurvey.org/review_92574.html . He doesn't mention any scale factor other than "huge".
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