I just installed Swanstone tub wall panels in the past two weeks. They are 1/4" thick. (You'd think they'd tell you this somewhere, wouldn't you?)
Another thing they don't tell you is to install the two-tiered Corner Soap Dish BEFORE you install the corner molding. The directions tell you to install the single tray Economy Soap Dish AFTER you install the trim. I assumed it would be the same for the Corner Soap Dish. WRONG. So I spent last Sunday cutting and filing the back corner of two of these so they would fit over the corner molding.
BTW, Don't assume the panels are cut perfectly square because I found that one of mine was wider at the top than at the bottom. This might matter if you have to measure in from one of the sides to do some cutting.
I'm by no means an expert, but having just finished a Swanstone tub panel installation and about to begin a shower panel installation, I'm willing to share my lessons learned. Feel free to ask.