Motor Plate/Water Pump Leak Issue

I've never had a problem with mine. I have a Mezziere pump with a home made backplate that is 3/8" thick. I use grade 8 allen heads with a flat washer and just regular gaskets.

Is your plate mounted to the stock front frame rail? Maybe that's the difference as the plate is larger with less support at the top to keep it from flexing. Mine is rather short with mounts pretty high up.