Well make from 3/4 x 1" stock a frame and screw it against the ceiling and you're able to slip in a filter. The RV industry isn't perfect if you want perfection the simple solutions is "Do It Yourself"
2014 Ram 1500 CrewCab 4x4 5.7 Hemi 3.92 Rear and Air Lift 1000
2005 Jayco Jay Feather LGT - 29Y GVWR-6500 lbs.
Pro Series 1200 lbs. WDH with Double Sway Bar.
Champion 3100/2800 watt Inverter/Generator-Onboard Solar Power
ALJO 'Forever Young @ Heart' provide on their travels Music Entertainment to Senior Care Homes