[GORDON HUMMEL]

Through trial & error I have found that the insulated AC ducts used in my Newell, cut airflow by about 50%. Before I installed the front roof air, I depended on the original Dometic unit. The evaporator is mounted under the forward dinette seat & then goes up the wall & terminates in the cove.
You can see from the picture below, there is a hole to the rear of the speaker, right of the thermostats. You can imagine that with the cove cover in place very little cold air makes it to the living area. I redid all the ductwork in metal from the blower to the vent. It took 2 elbows at the top to get it to fit properly. There was room for the the old lights, but just barely. Now that LED are installed there is plenty or room. One other point: I had to change the spot lights under the cove, because the old ones stuck up into the cove.

I also did the center AC ductwork in metal when I was redoing the pantry. I also moved the register out & turned it 45 deg so it would cool something other than the microwave. People in the co pilot seat complain that it blows on them!