We are on our second Grand Design, started with an Imagine travel trailer and now a Momentum 350M 5th wheel toy hauler. As said above, Lippert axle seals have been a problem, and I have had that problem on the Momentum. Other than that I haven't had any real problems with either one. And I can tell you first hand that their customer service is second to none. Everything that I have called about they have provided me with answers needed. I also needed some parts for the Momentum due to an incident that was my fault, they sent them at no charge. I have talked to several people on the phone and in person, including Don Clark the President/CEO, everyone has been friendly and helpful. As far as the frame, I accidentally lifted the rear of my RAM dually off the ground with the 5th wheel pushing the wrong button in the dark. No damage to the pin, frame, or even the hydraulic legs. So I think the undercarriage and components are strong enough, but I don't recommend putting them to that kind of test!!