Modified BBA Basic Sourdough ... Higher Hydration

On Saturday 1-17-2015 I baked this loaf. As I've mentioned previously I've been tinkering with Reinhart's BBA Basic Sourdough recipe. For this bake I aimed for 77% hydration:

10.2 oz preferment, 70% hydration

20.25 oz flour:

   1.5 oz Arrowhead Mills Rye flour

   1.5 oz Arrowhead Mills Sprouted Wheat flour

   5 oz KAF AP flour

   5 oz KAF White Whole Wheat flour

   7.25 oz KAF Bread flour

16 oz water

0.5 oz salt

I mixed the flour and water and autolysed overnight. I then mixed the preferment with the shaggy mass and added the salt. I kneaded with my Kitchen Aid for a total of 20 minutes using 5 minute kneading intervals with 5 to 10 minutes of rest between.

I let it ferment at room temperature (65dF in my house) for 2 hours, then put it in the refrigerator overnight and most of the next day; in the evening I stretched it out and formed it into a ball and put it back in the refrigerator overnight. The next morning I removed it from the fridge, did the final forming into a boule, and put it in a brotform dusted with white rice flour. It stayed in the kitchen for about6 or 7 hours to do the final rise (picture attached), then into the oven set at 550dF with ice cubes in a pan for steam. The boule was baked on a Pampered Chef pizza stone.

Side note: I have not independently verified the temperature of the oven.

The loaf baked for about 20 minutes at 550dF and then 475dF until finished.

Crumb shot also attached.

The loaf is delicious however I was not happy with the oven spring. I did some thinking.

1. I am not sure my steaming method is optimal for my oven (gas fired and vented).

2. As I've mentioned in several recent posts, I received a copy of Forkish's FWSY and I am considering using a DO.

3. My slashing technique for boules is not correct ... I was using the "angled lame" approach for batards which is not correct for boules.

I am now looking for an inexpensive cast iron DO ... I am looking to borrow someone's to try it out before I spend $50 on a new DO. I have several ceramic DOs, and I am considering using one as a "cloche" (I am concerned that if I preheat one of these to 500+dF and I drop in some dough that it will cause the DO to crack).

Next loaf will be 80% hydration.

Question: what are your thoughts on proofing? Does this loaf seem underproofed? I'm still getting used to the brotforms, which has been a significant change from the batards I was making using a jury-rigged couche system. I am a bit unhappy with the tight crumb ... I know it is mostly the result of my kneading process, but could the crumb be a bit more open if I let it proof more? Note the bottom of the loaf, the crumb is a bit dense. Opinions are welcome/encouraged.

Cheers-

Dave