before i had my cover on i would always toss stuff in the bed, (football pads, backpac, shoes) as long as you keep your tailgate closed you should be fine. the only thing that ever flew out of teh bed of my truck was a recliner. thats only because i didnt tie it down as well as i should have. the locals didnt really like dodging a chair as they drove down main street.

 

I have a problem with beer cans flying out. I just can't seem to keep them in there after i finish them and chuck them thru the rear slider.
Nah I'm just kidding most things will stay in the bed unless they are really light and the wind may suck it rtf out.

 

I once had a christmas tree fly out the back of my truck on the highway, but thats another story