I fixed a set of valve covers/breathers/baffles for a friends engine with cast alum covers that turned out as well as could be expected. I used stainless steel, counter sunk phillips head, 10-32 machine screws, with lock nuts, drilled completely through valve cover. I put just a dab of sealer in the hole before installing screws. Looked good and didn't leak. I also used a small spacer between the baffle and the valve cover to be able to use a push in cap and rubber grommet. CAUTION: make sure you have enough clearance between baffle and rocker arms, BEFORE you drill and cut!!

Brian