8 RCA? Maybe more space available above the upper pcb, not sure. 13 mm heigth, 19 depth in the A-E potentiometer area (on the left).
Maybe enough deph for 4x 6.35 jacks on the Master Volume area (on the right). Probably tricky to put back the upper pcb after.
Anyway I think the best is to unmount it to check what’s the best for you.