to make your life much easier. I would use a heart-shaped bur aka
156C of 012 or 013 size. don't drill a seat too deep into the prong,
why not? this is because each prong has to hold two stones at once.
So how far down the prong must you make the seat? The answer is
relatively easy. low enough that there is enough metal to push the
metal over the girdle. Now the best part is how do you set each stone
or attempt to move the prong. with a bead-burnishing tool. please
make allowance for the pavillion to sit AGAINST each prong. avoid
sitting the stone too deep into the space allowed. you need to have
the girdle exposed. the bead-burnishing tool MUST BE LARGER than the
prong-tip. you must push the prepared prong directly in between the
prongs, not at an angle. this setting is called.."shared-claws or
prongs"..each prong is being shared for security..
I hope that this makes sense. wishing you success!