Also keep in mind that if you decide to go the DIY route and make your own from foamboard that while it will improve airflow some it is not as effective as the RV AirFlow product. Maximizing the air flow is obtained by having the least amount of restriction in the ductwork which the curved plenums in the RV Airflow gives you and the DIY doesn't.
Also the more airflow returning back into the AC return air plenum equals more airflow out of the cold air plenum and into the RV.
If you notice, without any modifications to the factory setup that when you pop out your filters to clean them only half of each filter is dirty. That's because the factory system blocks approximately 50% of the return air vent limiting the total square inch area of filtration and return air flow... the DIY system does very little to correct this problem as it still blocks half of each filter.
Once I installed the the RV AirFlow products my volume of warm return air double and my volume of cold air supply increase dramatically...by almost 40%. Now when I remove my filters to clean them both halves of each filter is equally covered and I actually have to clean them way more often due to the increased airflow throughout the system.
Many people say that RV AC systems can only increase inside air temps by 20° above outside air... since I installed the RV AirFlow system I can easily surpass that 20° differential even during a heatwave.
