I've put the beans or chick pea on top of the shot, seems easier for me. The dried Goya beans don't crush. When I use cherrios I get crumbs along with powder and shot all over the place. The shop vac is handy.
Adding a bean also is easier than adjusting the cam on the Mec loader if I'm doing a few shells. For instance the AA shells crimp fine, but if there are a few Super X mixed in, I add the chick pea.
I'm not to the point yet of testing the pattern of a chick pea/bean shell vs a normal perfectly crimped home loaded shell. For me, I can miss the targets just fine either way
Left Shell - no pea
center - crimped with pea
right - pre crimp