I saw foam core blocks that you could purchase and put in the bottom of these air conditioning units to more efficiently move air through the system. The blocks were expensive and they did not make one for my particular application.

I bought some parts and supplies at Home Depot and hacked my Air Conditioning ducts for way more efficiency.

My coach is a 2008 Fleetwood Revolution LE. I have 2 rooftop Air Conditioners that feed 10 ceiling vents.

Under $20

1 roll Aluminum Foil Tape
1 Insulation Foam Core 1″ thick
1 Can Spray Foam Insulation
1 small handsaw (looks like 1/2 a hacksaw)

The handsaw
Exacto Knife
Phillip Screwdriver

Time to complete:
Less than 1 hour.