Quoting JNR:
Curious what the benefit to chopping off 50% of the baffle? If it's to clean in between, steam works awfully well with it intact /ubbthreads/images/graemlins/grin.gif Otherwise, would perforating (series of holes) be an option for somebody? Not for me (I cleaned mine already), just thinking out loud...
Steam might work well, but if the valve cover was sandblasted and the powder coated then there will be residue in there that you just wont get out without removing it. If you don't get the valve cover thoroughly cleaned of all blasting/coating media then it can possibly contaminate your oil and ruin your motor. It's fairly common to completely remove all baffles and not replace them when adding extra crank case vents.