Yes, well, I had thought about attaching a set of steel thimbles to the bumpers fore and aft, and basically building a set of steel-tubing ladder racks that I could cotter-pin into the thimbles when I wanted to haul the canoe.

When I didn't want the racks on the car, I could pull the pins and stuff the racks in the garage.

...when I get a garage...

It's looking like a more permanent kind of rack system is in order; thanks for the input so far, folks.