Indy messed up on those covers when they forgot to add a little extra material for screw in fittings. All they need to do is thicken the casting in a couple of spots on the cover so a person can drill and tap for a #12 o-ring type fitting. They should also add a few cast in bosses on the underside that can be drilled and tapped for screws to hold baffle plates. You can add all of that stuff but it requires some work.