Check to see if your crown bars still have a crown to them. If it’s a deck that you won’t be using for sizing/scalping, I just use “cheaper” 3-4” opening, 1/2” diameter woven wire screens and urethane crown bar strips. They work to keep the screen box tight and square. And they will last a long time. Depending on how much wear they have, just having a metal shop shear you the appropriate size of sheet steel and weld the new pieces to the side of the existing bars. It will help you tension the box and prevent it from breaking itself apart. I run Flexmat screens on the top and middle decks of my 5x16 and 6x16 gravel screens, and the mentioned oversized screens on the bottom deck.