i don't have sealant between my canvas and van body. have only seen it leak once and it was when i was doing 75-80mph on the freeway during a torrential downpour. even then, it was very little moisture that made it into the cab. one square of paper towel was more than enough to dry it up. i do plan on putting a bead between van and canvas, but haven't got that far yet. i cant say with other chassis' but with the econoline, the way the roof is shaped makes it pretty hard to leak inside under the canvas (unless its wind driven or forced under the canvas somehow). all areas where canvas is affixed to van roof aim downward from canvas so it just runs off naturally to the rain gutters.
interesting about the fixed tops and flexing. had never really given that much thought, but seems like a valid issue. has anyone personally seen a fixed top stress crack from chassis flex? i know the van flexes quite a bit. when are out in rougher country ive seen our dome lights come on quite a bit which means the chassis is flexing enough to move the doors far enough away from the switch that tells the dope scope to go off when doors are shut. seems like a pop top would be a better match for someone really getting out in the sticks and flexing the chassis a lot since it just basically floats up on top and can move around as needed.
