Most scales don't even log/alert/flag weights below the maximum legal axle weight or axle group weight. So a 2-axle truck can weigh 40k and nobody will hear about it. In the event that they're fancy and integrated with an ALPR (assuming your plate is readable, lots of ways to game that on a box truck) the scales don't typically extend onto the paved shoulder. Even if they do you slow down and drop a tire off the pavement. And if all that fails, if you have air suspension you can dump the axle as the truck is going over the scale.