I installed the RV Airflow in one of the two A/C units last year.
The fit was not as good as I felt it should have been but their customer service was great. They made some minor changes after sending them some pictures and videos. They sent me the changes in a few days and it fit much better.
There is a noticeable increase in airflow from the ceiling vents now that the unit dump vents are completely sealed off. But I agree it is only marginal quieter at best.
I installed mine in the front A/C unit so that it would increase airflow throughout the coach so at night I would not have the noise of the bedroom A/C running right above us.
It worked as planned..... both units run during the day but even on the hottest days / nights we can get buy with just the front A/C unit running at night to keep the coach cool enough now.
This was the final upgrade I did to my A/C after insulating the evaporator enclosures on the roof and improving the ceiling ducts. I think the RV AirFlow was worth it for one A/C unit but I can't see the need to add one to the second A/C.
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