wheel well back plate

I need to replace the back plate on each of my wheel well....do most people just use a pressure treated plywood or someother material with carpert attached? This is for a Stratos trailer

I took a pc of 3/8'' regular plywood and sealed it good with a thinned polyester resin so it will soak in good then used stainless staples on the carpet...it has held up better than anything I have tried. http://www.bassboatcentral.com/smileys/thumbsup2.gif

Mine is aluminum 3/16", carpet is glued and it is pop rivited to the fender.