Thanks all. My trailer is 23 ft (box) so alone it is plenty short, its the combo I'm worried about. The website says overall length of 40 is max. I'm going to back the truck up and get a no kidding overall length. Once I get backed into the sight I can unhook and loose most of the tongue length of the trailer so I'm sure I'll be able to fit.
What is at the back of the sights? Do they just have curbs, or are there poles? If just curbs why couldn't I just overhang the back of the trailer over the curb and have plenty of length?