[busterbrown]

Last year before I bought my Keystone Bullet, I looked at some entry level brands from different manufacturers that had the same wall panels in the shower stall as in the rest of the coach. I'm sure the laminated coating on the panels makes them ok for water resistance. But the wife and I decided to only invest in a unit with a dedicated vinyl or plastic bathtub wall surround. 3 young kiddos on board taking multiple showers per day was the deciding factor for the surround.

In your case, depending how much you'll be using the shower, you could apply a quality grade exterior paint to the panels for waterproofing and "lightening up" the space. I wouldn't really consider a water sealer on a finished panel.