Bakflip hd leaking

I got a Bakflip HD and installed it. It leaks like hell, even with simple hose washings at home. I don't quite understand why you have to install the "drain hose" if it leaks all around the the damned thing. Any suggestions on how to prevent leaks ?

 

I took my rails off and removed the cheap thin weather stripping that came on them. I went to Lowe's and got some thicker heavier duty stripping and put them back on the rails. Mine still leak a little but not as much as it used to. Because our trucks have the Composite bed liners, it's close to impossible to get a watertight seal. If you look at the bed rails of our truck too, the bed doesn't have a uniform shape; therefore making it impossible for the Bakflip rails to fit properly. The hoses are just there to drain the water out of the brackets of the cover, not to keep water from leaking in your bed. I hope this helps.