Do they exist in adjustable or shorter lengths? I thought I had seen a strap or bar that connects from the bed to the tailgate and allows the tailgate to remain partially open. I am going to be hauling 3 bikes in my truck and towing a trailer. With the 3 bikes in the bed, I will not be able to angle the bikes to make the tailgate close, and I'd prefer not to have the tailgate open while towing. The bed is long enough that the wheels will not be resting on the tailgate, but not long enough that I can completely close the tailgate. Appreciate any info!