I have an 18 ft. fiberglass sea-kayak, which I mount to the roof-rack of my junky old station wagon with Yakima "Sweetroll" saddles - ratchet straps around the saddles and bow and stern to the bumpers. Unfortunately, while on a recent trip I suddenly noticed a 3-inch crack materialize in my windshield, which rapidly grew to an 18-inch crack.
I didn't see any impact that started the fracture and no part of the mount or the straps actually rests on the windshield - so I'm concerned it was the tension of the bow and stern guy-lines flexing the roof and putting too much pressure on the glass. The windshield is fixed, but I'm a little gun-shy about putting it up there again. Is there a better way to distribute the pressure on the roof? Should I just not ratchet the bow guy line down as hard? (I generally ratchet it down pretty tight to keep the strap from vibrating madly)