passing vehicles with the trailer

Some of them still do. I think it is about 50/50.

What I generally do is use my towing mirrors (you do have them, don't you?) and my depth perception to see when the end of my TV+trailer is 1 or more lengths in front of the passed vehicle.  Then I signal and check the mirrors again.  THEN, I move over into the other lane.

The other visual clue is the 16-30 year old driver who tailgates you as you pass then zips into the gap between you and the passed vehicle and gives you the finger as they pass you on the right side. 

Sometimes shadows of the passed/passing vehicles can help. 

Used to be that semi drivers would flash their headlights at you when it was safe to pull back into their lane.  This generation of truck drivers evidently don't know about that courtesy.

I had the idea after our first outing with our R-pod and not being able to see what's back there.  I found a Peak wireless backup camera in the clearance bin at Menard's for $60 and took a chance it would work.  I attached it to the license with some metal strap.  Removed the license plate frame from the R-pod and spliced the power to the camera into the license plate light and reattached it to the R-pod.  The lights on TV have to be on to power the camera which is okay because I drive with my lights on on the highway anyway.  The monitor is plugged into a power port (formerly called cigarette lighter) and stuck on the windshield.  Viola!  I can see what you're doing back there, so behave yourselves!!!  

I installed a rear view camera on the license plate of our 190 and it's a great help with lane changes, backing and just seeing what goes on back there.

Furpod has an excellent suggestion with the use of a rear camera. I hope one of the future improvements on the R-Pod with be at least they putting in the wiring to mount a rear camera as they now do in the Jayco Hummingbird. You may want to look into adding on rear view mirror extenders that will give you a better sight view to the rear.