Generator side box

That looks like a nice enclosed setup to help keep it quiet and keep road grime out. I'm not sure about the DB rating, if it compares to the Honda or Yamaha rating using similar testing methods it's probably a good deal assuming it lasts.

One thing I had to do every 500hrs or so was pull the spark arrestor and clean with a wire brush and gasoline. It plugs up with soot if ran without a good load. Not sure if this model does the same thing but something to watch.
I'd be careful about trying to seal it up or re-route the exhaust. It's easy to overheat a machine without ample fresh air and free flowing exhaust.
I've never noticed any fumes or smell from a Honda unless the spark arrestor was plugged, then it pumped out oil and a plume of white smoke.

 

I also wondered if you could run a longer straight pipe out the frame rails to the rear.

Does a longer exhaust reduce noise, or do you need another muffler (restriction)?

 

Any addition to the factory exhaust will likely reduce noise. You need to be careful not to restrict the flow with small diameter tubing. You could try a few different setups using scrap materials and check temps with a laser to see if you're overworking the engine by restricting the exhaust?

 

I've seen stealth exhaust systems for four wheelers designed for hunting. Maybe reverse engineer one of those?

 

The run times are interesting on these.

The Honda 20 hours at 1/4 load
Predator 11 hours at 1/4 load
Champion inverter 7.5 hours at 1/4 load

‘Sound levels are all close, Honda twice the cost but best reputation, predator has some great reviews on YouTube and cheapest, Champion inverter makes some good stuff at can be had less than $1k.

I have a 6500 watt Onan gas from an RV that is crazy quiet but it has some power issues at this point and is quite heavy. If it was diesel it would be worth getting fixed.

Blair trailer has the gen mount on the left side down on the trailer and is quite always back from anyone. I just can’t see anyone #####ing about the noise. But then again... truck drivers will find a way. The last thing I am worried about is a bit of noise. I sleep like a baby at truck stop. I guess my years at sea in the Navy with aircraft taking off and landing right over my head depending on what berthing I was in prepared me well. Lolol.

 

A couple of thoughts here.
On a gravity fed carb wouldn't adding extra fuel cause a rich fuel mixture? Or until the weight of the fuel is reduced.
Why can't the exhaust be tied into the truck stack?