Pictured above is the first boule... of many attempts... that I've made that hasn't involved lots of burning. As mentioned previously, this is mainly because I'm a stubborn idiot who has refused to change his baking tactics even when it's clearly not working.While I do fine with baguettes and smaller loaves, the large size of a boule, and thus longer cooking time, has always done me in. Eventually I became frustrated enough to look for tips and settled mainly on the (fairly obvious) solution of moving the baking stone up from the bottom of the oven. As you can see, this worked pretty well... though it started to get a little over browned while still not nearly done, so I needed to scale back the temperature quite a bit (from 475 to 350) after about 15 minutes and cover the top with foil to avoid burning. Next time, once it's clear that a good crust has formed (10 minutes?) I would probably pull back the temp to something like 400 degrees... maybe cooler.
I used the same formula for Pain a l'Ancienne that I've used successfully in the past, but simply shaped it into a boule, instead of baguettes, after the dough spent two days in the fridge. It's still not quite as airy as I would like, but the higher hydration relative to your basic French bread recipe did make a difference. I think I'll just keep pushing the limit until I figure out the wettest dough I can handle and effectively shape into a boule.