I don't know if you have a bed liner and a tonneu cover (hard to tell from the little picture), but here's a tip for weight if you do:
Personally, I have no need for bags of sand that I have to store every summer, so I purchase about 6 bags of water softner salt to place in the bed. Because of the bed liner and cover, I don't worry about the precipitation melting the salt and damaging the bed. Have done that for the past few years, and when spring comes, I just put the salt in the basement, and it usually lasts me until I need more in the fall (when I buy enough for an entire year again).
Of course, if you don't have a water softner, this idea isn't very good for you at all!