Franklin Quick Change Help

I have an 02' GRT with a magnesium QC. Problem is the previous owners put Heli Coils in for the rear cover. Couple of weeks ago I broke a gear set and blew the cover off. We replaced a couple of the heli coils but still can't keep the cover from leaking. Is it possible the cover got tweaked? Is there a way to fill the holes and replace the heli Coils? Tired of buying gear oil!

I learned the hard way about the Frankland covers. I filed my cover down with a flat file and tightened the cover with less ass than I used to tighten it. The thing never leaked through a rough race and I stick to the 2 important things. File the cover and don't over tighten. All of this is dependant on good threads to pull to.