Your dash air on any motorhome will only be comfortable if you can control to some extent, the area being cooled.
Some type of barrier curtain is a must to be comfortable on those long drives into the afternoon sun.
The system does not have to be complicated, but it should go to the ceiling, and should overlap at your entrance so that it slows the air exchange with the main body of the motorhome.
I run with the bylevel Air, on MAX. but the fan speed set to slow, once the cabin is initially cooled down. It is quiet, comfortable, and the barrier curtains are only pulled back all the way when the TV is to be watched.