Thoughts on combining Tartine, bran levain and Artisan in 5?

I am going to attempt this for fun and to see if I can get those nice big holes which I am going to get one way or another with a whole grain bread. I can do it with recipes who have a high percentage of AP flour but the crumb tightens right up when I go for lots of whole grain flour. I am hoping I will have better luck with this one. If anyone sees any glaring errors in my method or you have thoughts on this, please let me know. Thanks in advance.

The recipe is Wheat-Rye 20% Boule from Tartine 3. Levain method is per DaBrownMan and method is mostly from Artisan Breads in 5 minutes and their website plus a few Forkish folds thrown in for good measure.

1. Sift whole-wheat flour and rye flour to extract the larger pieces of bran. I obtained 25 g of bran for the levain.  Recipe has 287 g high extraction flour (reduced 113 grams from recipe because of the increased amount of levain- see below), 200 g dark rye flour and 100 g whole wheat flour as well as 300 grams of all purpose flour.

 2. Use bran and high extraction flour (locally milled partially sifted flour) to make 3 builds of levain, each 4 hours apart. Build one: 25 g levain/25 g bran/25 g water. Build two: all of levain/50 g flour/50 g water. Build three: all of levain/100 g flour/100 g water. Total 375 grams of levain as per Artisan in 5 (They suggest 1.5 cups of sourdough starter which is ~375 g in weight.) (Tartine’s original recipe called for 150 g levain so I removed 113 g each of flour and water from the main recipe). Let rise 25% after last feeding and put into fridge for about 24 - 36 hours.

3. Pull the levain out of the fridge and let it rest at room temp for 2 hours until it rises about 25%. May need to put in oven with door cracked open as my room temperature is 70-72F.

4. Meanwhile, autolyse 287 g of high extraction flour, 300 grams all purpose,  200 g sifted rye and 100 g sifted whole wheat as well as 70 wheat germ. Mix with 687 g (reduced 113 g because of increased levain) of 90 to 100F water. Let autolyse for 2 hours at 70-72F.

 5. Add all of the bran/flour levain, ½ tsp yeast, 25 g salt and 50 grams of water. Pinch and fold until fully integrated and the dough develops some structure.

6. Do 3 sets of stretch and folds in the bucket 20 minutes apart for the first hour. Let sit until it rises almost to the top of the bucket and starts to flatten out. This could be another hour or up to 12 (as per Artisan in 5 website when you change or reduce the yeast). Time only will tell. Put into fridge until ready to bake, minimum overnight. Dough should keep at least a week, probably 2.

7. When ready to bake, take dough out of fridge. Divide the dough, pre-shape, let rest 20-30 minutes and then shape it into boules and let sit for 60-90 minutes in proofing baskets that are dusted with brown rice and AP flour.

8. Pre-heat oven to 500F for 45 minutes. Put loaves into hot Dutch ovens. Twenty minutes later, lower temp to 450F. Remove lids at the half hour mark, and then bake uncovered for 20 to 30 minutes.