I had the same problem with my primary plate after changing the primary oil. Put the plate on and was torqing to Big Dog specs, and the top corner broke. My next inspection cover, Replacement, I didn’t torque as tight as called for in service manual. Snugged it down in the proper order called for in and no corners breaking or any leaks. As far as a reinforced cover or a cover with a grove in it I don’t know of one.