Had stable loads on our 2008 Denali 1500. All they do is engage the overloads sooner when engaged. They do not add any extra support. I put timbrens on our2015 Denali 3500 and couldn't be happier. They act the same way as adding a extra overload springs or airbags, just not adjustable. Towed without them for the first 6 months, about 6,000 miles and with them since. At least 15,000 miles. We had a cap on the truck and a bed slide which together add around 500 #s, so the timbrens are within a 1/2 inch of being engaged even without the trailer. Neither I nor the wife find them objectionable. Just my vote for the timbrens.