We didn't keep any heavy stuff under the bed. From now on, we are not placing anything under there. We did add a 3" foam mattress on the original mattress. I wonder how much force is exerted on the back slide wall when the slide is operated. I am going to reinforce with "L" brackets and attach to slide floor and frame of bed. Just wondering what the back slide wall consists of that can be reinforced with more screws and a larger wood piece across the head of the bed frame. I don't think "rocking" did it! More like 25,000 miles of highways it has been over. Any more suggestion appreciated. Thanks,