i replaced my roof. there is about less than a 1/4 gap between the roof and the braces. there was some type of sound deading material that goes inbetween the roof and the braces. you really should not have much flex from the roof at all. the roof should have some flex but not much. look for a dent that could be the culprit or the roof is not squared to the body and there might be some tension in that area. i would tack the roof in four points first instead of the rear only. i forgot to say the body must be braced up straight