Look at small fiberglass trailers like a Scamp, Boler, Armadillo or a Snoozy. The forum at fiberglass RV.com has a lot of information. I have a German Eriba Puck I imported from the UK last year - it's 12' long and weighs around 1000 lbs.Thank you again for the feedback. The Front Runner rack on my LR4 was quite loud, but the fairing I installed quieted it down considerably. I see one of your club members has the Front Runner rack on his Defender as well. I had a similar experience to Dogpilot, and the purchased separately, at considerable expense, Front Runner fairing did work well. I was curious whether a Land Rover designed rack would be quieter since presumably they could test it in their own wind tunnel or as part of their own Defender testing, but I suspect that there really is only so much one can do from a physics standpoint to get a reasonably quiet roof rack. I think that a front fairing is really the best bet, but I also find wind noise to be annoying and fatiguing more than most.
We are considering a small travel trailer, but it would probably be 2-4k lbs, so similar to your experience. That's helpful. I really would prefer my vehicles to either be fully internal combustion or fully electric at this point from a complexity and drivability experience, so it's good to know that the P300 would fit our needs in the future.