In the spirit of learning from other's trials.
Here is a picture of Ed's original system.
Problems in this picture ignoring the scoop, duct type and size 
for the moment are:

A. Cooler appears to be too close to firewall to allow air to freely 
escape out the back side. The picture may be deceptive on this.

B. Transition from round duct to cooler is not a smooth bell shape.

Ed, I vaguely recall that you improved the transition from duct to cooler. 
Did you? If so do you have that picture?

Paul Lamar
 
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