The only detrimental exposure to the "elements" that has occurred to my playing card trap is from the element Pb, and is a result of my poor aim. I use the traps mostly indoors or on the screen porch, taking them outside only when the weather is nice. I would suggest a front edge 45-degree bevel so that errant shots strike a glancing blow and deflect inward, toward the trap face rather than bouncing straight back. With a 400 FPS SPP pistol at more than 5 yards, the rebounding pellet wasn't very dangerous, but wearing eye protection, as always, is a must. A higher power pistol shooting wad cutters would be dangerous at close range for this reason, and in my estimate, requires no less thann a 10-yard shooting distance (at which point, I would probably be switching to the larger target anyway, especially with a pistol). I might also suggest you cut the slots to hold the target at least 3/8 to 1/2 inch deep from the face of the target to prevent errant shots from splitting off the front edge of the wood.
With all that said, I LOVE these pellet traps. Weighted with duct seal putty, they are rock solid and perfect for us indoor pistoleros. You're not getting my two traps back! And I am still looking for that new model to hold a cut-out clipboard. It occurs to me that the safest way to use the clipboard is backwards, presenting the pasteboard face to the shooter instead of the metal clip, and using the cut out clipboard a s a frame for the target behind.