I have a 2017 Quantum 31S with the superslide. We haven't had any issues with leaning or instability when the slide is opened. We just follow the instructions and do not open the slide unless the leveling system is down. Their is very little weight that is added to the slide when it is opened on ours as the only thing that may be outside of the truck chassis is part of the dinette.
Kelly and Jerry Powell with Halo (Lethal White Aussie), Nash the Rat Terrorist, and now Reid, the "Brindle we have no idea puppy"
2020 Grand Design Solitude 390RK-R