Kevin & Kristijan!
Take a breath! What we are talking about in wet filtering is: 2 sheets of matress,
each 3-4" thick laying on each other, length 1/2 of an adault person’s length; that means a full matress cut in two equal pieces. Has to be open-cell foam, medium heavy.
That will do for a 4-5 liter motor.
For a car with ~2 liter motor a ski-box gives very good room. As the gas goes up and down from behind, relatively cool, the flex-tubes can be camouflaged by “fancy fins”.
Then generally, the gas has to pass from below up on the upper side, to avoid ripping water in drop-form.
Kristijan, you cannot compare two quite different situations with vastly deviant passage areas for any filtertype!