A good way to check is to hold a length of tissue near the vent, then have someone else block one of the near vents or more. You should see noticeable deflection with some vents blocked. If you play with the blocking you might be able to produce a better more even flow.
Mike
2012 Winnebago Impulse Silver 26QP
2005 16.6 Double Eagle
2018 Jeep Wrangler JK
previously Snowbird Campers,
Triple E Motorhome and Fifth Wheel