I tried to find a pic of one with the same poor design but I couldn't. Here is how it should be - round plate should be flat all the way around where the rim of the screw heads meet the plate. The old one has notches on the outter edge around the screws making it impossible to seal around screws.
On the new unit I bought the screws have some sort of teflon coating around the rim allowing it to seal around the bolts. I still can't get s few of them real tight but the instructions say they don't have to be very tight. Only tight enough to compress the seal around the screws. I have 1 that is stripped out pretty good, and 1 or 2 more moderately stripped out. Seems ok now but the real test will be upon next fill up.
Stock Interweb photo:
