I am in the process of assembling my motor.I would like to avoid future leaks around the valley cover.I have seen mentioned on this site that some of you have added extra hold down hardware.Are you drilling and tapping for bolts or just drilling and using self tapping sheet metal screws?Where are you adding extra bolts?Just the 4 corners or?My cover does not appear deformed from over tightening but it started to leak not too long after I changed it to install PCV system.Would like to modify it while the motor is apart to avoid future leaks.