Miles....I just purchased a 36' Monaco Diplomat. I was also told that it may not ride well because of the wheel base. This is my third motorhome and it rides very well. I've never driven anything longer than my current wheelbase, but I don't feel any unusual bounce.
My coach weigh 28000 pounds and has the 400 Cummins. It's moderately loaded and only occasionally will move around alittle if it's hit with a good gust of wind.
It has the Roadmaster (8 airbag) system and Monroe shocks. It has fairly short, but wide Goodyear tires compared to my brother-in-laws Itasca Meridian. Finally, I don't go crazy on tire pressure (keep it right at the axle weight recommendations). I think all of this makes this coach ride very well.
Don & Mary
2014 Newmar Dutch Star - All Electric - 450 ISL
2016 GMC Canyon 4WD Crew Cab