This man above is a legend in Boston/Cambridge. He always has this much cargo. I am grateful to not carry this much gear on my bike.
When I do need to transport large quantities of stuff I'm very impressed to learn that the representative in Cambridge has an extracycle he's willing to loan out to citizens who give him just a bit of notice. That seems like the perfect application of an extracycle, and a very good PR move on his part.
Our friend Max moved house in Cambridge before this loan was available. His photos now grace the homepage at Alterna Transport.
Finally, if you're the type who would have otherwise bought a pickup truck (because you carry so much), consider instead a Yuba Cargo Bike.