Don't have any experience on this in an MB Class C but I guarantee that any Ford V-10 will keep the entire coach of a 24' Class C nice and cool eliminating any "need" to run the house air. I live in southern Arizona and we use our coach extensively year round in temps up to 115+ and have never had an issue with the dash AC getting the job done.
If it is going to be excessively hot we just open the rear Maxair hatch and run the fan on low. This draws the cold air from the front of the rig {the dash AC} and blows the hot air out. This would probably enhance the effectiveness of the Dash AC in a View/Navion. Our pooch {who has since passed over the Rainbow Bridge... sigh}, was always cool and comfortable lying on the rear queen as we traveled throughout the southwest.
IMHO: If you need to run the genny to power the roof air you should have bought a better coach.
As always... Opinions and YMMV.
:C