Simple math says you are wrong.
Face area of fan vs circumference of fan times clearance provided by stock feet (17mm) for intake.
15.38 sq cm fan area vs 7.47 sq cm intake... on hard surface, not carpet.
Raise case up so you have 40mm clearance and your intake area becomes 17.58 sq cm.
Raise case up so you have 50mm clearance and your intake area becomes 21.9 sq cm.
Add a 140mm intake fan for case in front of PSU fan and PSU fan looses 25% of it's intake area which means 21.9 sq cm is now 16.42 sq cm free access to airflow... Which is the reason I suggest 50mm
Technical fan area is just fan blade area without center hub/mother area; 15.38 - 1.26 = 14.12 sq cm.
But add in the airflow resistance for turning air 90 degrees from floor to fan, friction of air sliding on floor and case bottom, etc. and you can see why I'm calling a spade a shovel. Stock feet set case too close to surface.
Add carpet and... well... shall we say even more clearance is needed.