I don't personally love trailers, and prefer two wheels. On the other hand you will have the weight, and really if you are pulling 120, or 80 the exact method gets to be trivial. A third wheel probably has some advantages. Keeping the load low is huge, at the weight you are considering. The biggest advantage is you could probably get out there tomorrow, for about what the couplers cost on the frame you are contemplating. That would suit some.

I would still like to hear why the weight. Don't care if you are carrying bibles to the Congo, or vibrators to Kabul, but I would like to know if you are ignorant about camping trends, sorta crazy about carrying your comforts, or have a serious reason to carry a lot of stuff. Because until you clear up your need for so much weight, at least in generalities, you are looking a little crazy/ill informed, which may be far from the truth, like Kroop. No need to feed the doubters.