An ultralight airplane is an airplane. Like any airplane, it has capabilities and limitations and, like any airplane, it must be maintained and flown properly. Unlike a certified airplane it may be made out of any kind of parts, with any kind of engine, and maintained by anyone. Unexplained engine failures are far more common than with certified airplanes. I am almost surprised that one did not occur during our trip.
A lot of people would not take a little airplane like this on a 1600 nm international trip. I have experience not with long-distance ultralight flying, but with making long trips in little steps. I am always amused by responses like, "you can't get there by bicycle" or "it's too far to bike" when I ask people for directions to places within their own city. If you push the pedals, the wheels will go around. It works the same way two hundred kilometres from home as it does in your driveway. That was my view on the airplane.
Maybe it would be most sensible to take off and do simple flights in the vicinity of the home aerodrome for the first fifty hours or so of the shakedown of a new airplane. It would definitely be sensible to be very attentive to the break-in period. But the airplane, you see, does not know where it is. The airframe 'knows' that it took off, made some turns, flew level, made some more turns and landed. It can't tell whether it returned to its origin or not.
The engine can not tell that the first leg of our journey did not end where it began. It only knows that it was warmed up, given full power, reduced to climb and then to continuous cruise power for a couple of hours, before being reduced to approach power, and finally to idle and shut down. It 'knows' that this routine was repeated twice a day for a few days. It was always warmed up, never shock cooled, never run at take-off power for an excessive period nor allowed to become too hot during climb. It always had sufficient coolant and the proper level of clean oil. Perhaps it 'noticed' that the outside air temperature dropped steadily over the five day journey, but it never encountered temperatures it wasn't designed for.
The riskiest part of the trip was not the risk of crashing into the American countryside, but the risk of being stranded partway through the trip by a mechanical problem or by weather, with both of us needing to go back to work. A small mechanical problem would have been quite repairable, at the technological level offered by people who repair tractors and bicycles, but had we lost as much as half a day to such a problem, it's likely the hurricane would have caught us and we'd have to beg hangar space to hide in. The advantage there is that the little airplane could be secured in a hangar that was already 'full' of conventional airplanes. It could be tucked underneath and in between where other airplanes wouldn't ever fit.
I would not recommend a trip like this to anyone under time pressure as we were. It would have been a walk in the park had we the time to zigzag for destinations with interesting things to see, prearrange with people on the ground to meet us at the airport for food and fuel, and not done it during hurricane season. A chase vehicle would have been very advantageous, someone who would drop us off at the airport and then start driving and meet us at the destination. The airplane is not a lot faster than a car. Getting mogas took longer than expected. Advance time spent in research in advance on mogas availability would not be wasted. You wouldn't want to do it if you were not comfortable making decisions like "this part of the airplane needs to be cut off with a saw to avoid interference with the rudder cables." You have to be able to call the game when it needs to be called. I should emphasize that we were really lucky. We had no non-trivial mechanical issues. The sum total of our weather delays was five hours, one for convective activity and four for fog on two different mornings. Neither of us got sick or injured. No one ran over our tiny airplane while it was parked on the apron. I wouldn't bet money on flying eleven legs in the airplane I normally fly at work without a mechanical delay. I might bet against it. You must have time in your schedule to recover from delays. But if you do, and if you and your airplane can fly one three and a half hour leg into an unfamiliar airport, then you can do it again and again until you get to where you are going. That is what airplanes do.
I really recommend you don't do it during hurricane season, though.