I took my 69 Shelby replica off the lift ,it has been up there for about 5 months now . I tried the panels in it and they were loose at the hockey sticks .I added the insulation behind the panels like they are supposed to have and they fit nice and tight .Looks like they need the insulation to keep them pushed out at the bottoms because there is nothing to attach to at the bottoms ,the card board ones just float also ,but they did have a foam block at the bottoms on the back side to keep them tight to the hockey sticks and that would probably be a good idea for the fiberglass ones also . They look great ,except for a little dust ,and i will never have to replace warped card board again .