Cannon Balls

Hey TFLies,

My wife is a HUGE fan of the cannonball, and with my recent success in sourdough bread, she's requesting that I try my hand at them.  For those who may not know what a cannonball is (not the heavy metal projectiles), a cannonball (CB) is a small sourdough boule that has been hallowed out and had soup poured into it.

Now, I've never made CB boules before, so I'm looking for some pointers before I try to tackle this project.  I'm pretty sure a 6" boule/roll would do the trick, but without physically having a CB in front of me to measure, I can't be sure.  Further, I'm pretty sure the boule's used for CBs are much more spherical than many of the boule's I've made in the past, so there may be something there I'll need to do in order to make a very high dome.

 Again, any help from somebody who has produced CB boules would be greatly appreciated.

Cheers,
Taco