Adjusting time/temp for smaller loaves

Hi all, 

I have a great sourdough starter and have been making loaves with it for quite awhile, baked in an unenameled Dutch oven. I want to take a loaf worth of dough and divide it into four smaller loaves, to make sourdough bread bowls. I am going to try baking two at a time, on a baking stone, under an overturned roasting pan, as two won't fit together in my Dutch oven.  My usual baking is at 450 degrees, 30 minutes covered, 17 minutes uncovered. So, with two smaller loaves, any suggestions for adjusting the baking time? Seems like temp would stay the same? And perhaps covered time stays the same, too?

Thanks!

Jennifer