I had a 2017 29.3 ACE. It had a large single wall slide. We downsized from a large 5th wheel to the ACE. After a little over 2 years and 20000 miles we found out that we downsized to much so had to trade for a larger unit.
Anyway the ACE had only the one 15000 but AC. We found that yes two may have been better, however by covering the ceiling vents, and the use of a couple small fans life went on without much problem. My wife did make a very good reflective new front curtain. That help more than anything.
As for the rest of the coach, I had no major problems, some minor that happens through out travels. Make sure you stay up on oil changes and grease that kind of thing.
Itasca Meridian SE 36g
Road Master Tow Dolly