Jeff-dandare100

This is mine. Just took a piece of alu flat bar and bent the one end 90 degrees and bolted the other end at the fan side to the 3d printed fad mod. So it just hooks over the inverter.

 
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Both temps dropped by between 10-15 degrees. My ambient temp in the garage never goes above 15 degrees.

I have mine running the 4 fans at 11V permanently, the lower voltage is so that the fans run at a lower RPM, therefore theoretically extending their lifespan.
You can lower the voltage with two resistors R1=470Ω and R2=5.6kΩ connected like this:

from a normal 12 1A DC adapter to about 11V. [ref]
Replacements should be cheap if one fan goes.
Also agreeing here, electronic components favour cooler conditions.
Cheers

I think that it would be impossible for this setup to cool the inverter lower than ambient temperature so it could never harm only improve cooling to ambient temperatures.