Re slides in class c's and class A's .
The A's might be using hydraulic slides and the A's might have a little more beef in the framework of the coach where the slide slides. The headers on A's might have more room above the slide to build a more beefy header. That might be the reason the A's coaches seem to have less issues, especially flexing.
Remember not move a coach once you deploy a slide. I have seen people pull into sites and deploy the slide then find out they are too far away from the pedestal and move the coach back n forth to get closer and then level it...all with the slide hanging out . That's a good way to crack your sidewalls of your coach as well as possibly bind the slide it the frame.