I bought a used tandem axle trailer recently. I'm in process of re-burnishing it. While I had it propped up in air I removed all the boards to clean frame up. While the axles were suspended in air I noticed the sides of frame dipped in center slightly from the weight of axles hanging there. (keep in mind all boards are off)..now that it is back on the ground..it appears to sag slightly down at rear (oppisite it did suspended) But..The frame is 2"x 3" (3/16") rectangular tubing. Would not that be as strong as 5" or 6" angle iron frame? Is this because the boards aren't on there to help support the weight of the metal? There isn't a ramp on it yet- seems that will add to the sag? trailer is 14ft long. Note: no side rails added yet either- will be thou..their made, but not welded on yet.