Tote Gote BearKat motor plate question.??

Im hoping somebody will know about this BearKat motor plate,Richard or Davis...

What the heck goes in the large circle on all 4 corners and how would we install them?
My guess is 4 large rubber mounts?

The motor plate does not come out of the bike ?
Saturday Im going to grab a older 70s Briggs 7hp but now need to get this problem resolve. ..