Have you ever sat on the bedroom steps during the winter months and wondered where all that cold air is coming from? I've owned 2 Montanas and both have had a problem of an air gap in the middle of the bottom seal on the bedroom slide when extended. Although not much more of a gap than to see light thru, it does let a bunch of cold air thru that seeps around the base of the bed and on down the stairs. I have a pretty simple fix that'll keep the air out. I'm not worried about water as it's really a non-issue in the center of the slide seal. The board is a 1"X4" with some adhesive backed foam on one side offset 3/4" to allow you to screw the board onto the face of the plywood decking under the head of your bed. You might have to cut a relief in the 1"X4" to allow for rear cylinder mount clearance when the slide is retracted, you'll just have to check this depending on where they bolted the mount down on your unit. About the only other thing is be sure the hydraulic lines are secured away from this potential pinch point. The photos should cover any questions.
http://i113.photobucket.com/albums/n...lideBefore.jpg
http://i113.photobucket.com/albums/n...SlideAfter.jpg
http://i113.photobucket.com/albums/n.../BoardSeal.jpg