Your Georgetown may be different, but this may give you some ideas.
I installed insulation on the underside of my doghouse cover to quite things down. I also got some heat reduction out of th e deal.
Also, I found some large openings up near the firewall that was letting hot air in from the engine compartment. I used some expanding foam to plug these openings.
These two items improved the cooling capability significantly. When we do a trip out west in December, I'll know more if it improved the heating capability. The air leak was making the drivers side cold, and having the heater on full blast was keeping the passenger side hot.
Sound deadening and heat shield | 2001 Coachmen Mirada 300QB
Yes, we do run the generator and roof top AC while traveling when the dash AC can't keep up.