Realist, please forgive me if I have implied I built this trailer, as I did not. I have not built one yet, but do plan on doing so in the future. I looked up system on a trailer that showed what was used and where they mounted everything, along with the schematics like what you were looking for. As far as the set up in this particular trailer, I'm guessing they were wanting a higher voltage output, and I believe James answer beat me to the punch. And for the generator, I don't know, but a propane powered would work just as well as a gasoline power one. I was just trying to show how a larger solar system does not have to be tied to a home only. You can still pack quite a punch into a smaller portable package.
And after looking around today, I have decided to go with a wagon style platform rather than a 2 wheeled dolly platform. It won't be as top heavy, and it would give more room for the batteries. I also have decided on going with a 1000W pure sine wave inverter.