[hbens]

I installed a Pioneer 240volt 20k system with 2 12k cassette evaporators. I used the original SCS ducting to the coach mounting the cassettes in the return air plenum.
I wasn't satisfied with the cooling when sitting in full sun which is what I have here in my parking pad behind our house.
I used the heater ducts that exit below the console in the salon for additional cooling ducts. These 4 small ducts weren't providing heat so I made them dedicated to the mini split. This provided 2-3 degrees of cooling relief.
I added 4" inline fans to the elephant trunks in the front salon. This also added 2-3 degrees of cooling relief.
I added additional 4" inline fans to 4 of the rear ducts. I did this in 2 steps. The first provided another 2-4 degrees of cooling. The last 2 inline fans I cannot tell you with data how much they added. 
My SWAG (Scientific Wild A$$ Guess) was comparing the before and after when I had 2 very similar weather days prior to and after the installations.
Richard gave me the suggestion to add the fans to the rear to increase airflow there. 
I believe each time airflow was increased through the cassettes the cooling performance increased.

I plan to hang a 12k 115 volt mini-split in the bedroom most likely sticking with Pioneer. This should make the coach cool enough for anyone and allow us to stay at parks with only 30amp service. Of course power management will be a concern at these parks. The 115v mini-split will run off my inverter as well. I have 2 Subzero fridges so I have 2 inverters and no room above them to install a cassette there.

I like the quiet operation of the mini splits compared to the SCS units. Still, I would have preferred to keep the SCS units but when my transfer switch died it took out the SCS units forcing my hand.

Thanks to Jack, Arch and Richard for their inputs for this project. All you others who have commented with your experience(s) on our posts have also helped me.