Thule rack across truck bed, any way to decrease sag?

[snowfiend]

I got a new truck and am ready to install my Thule rack across the bed, but want to see if there is any way to decrease the amount of sag in the crossbars. Its fine unloaded, but even with two bikes on the rack it has a noticeable sag and the bikes bounce a bit. I would like to get either two more bike mounts or a basket, but am concerned it would be too much weight. And forget about a RTT! Any ideas? I don't think the rail caps help either since its not a solid surface to mount the feet on, but there isnt any other way to do it that I can think of. Here is a picture of the setup on my old truck, has a retractable tonneau cover under the rack:

 

[fortel]

How old are the crossbars? I ran a Thule rack set up for years carrying bikes and/or kayaks and don't remember any of the flex you are talking about. Mine was on a Ford Ranger so there wasn't quite as much distance between the towers as on your F150, but there shouldn't be that kind of movement. Might be worth a call or email to Thule customer service to see what they say. Look at the crossbars without a load and see if they have taken a set and are sagging with no weight on them. If so you might try flipping them with the bow/curve up and see if that helps. If all else fails you could rip down some wood to a fairly snug fit and insert it inside the bars and that might take some of the flex out.

 

[01tundra]

They flex......

 

[jeep-N-montero]

Semi rigid aluminum like those cross bars will typically flex a bit, pretty normal. If they break under normal use they are under warranty.