36% WW sour with Flax Seed Meal / Bran Soaker

Howdy y'all this is my first post on TFL but I've been following this site for almost a year now and it has helped a lot with my endeavors in yeast as I am very much still a novice. Anywho this is a 70 % hydration sourdough (If my math is correct) incorporating 36% whole wheat and a soaker composed of bran and flax seed meal. the taste is quite nice with the nuttiness of the soaker not overpowered by the sour despite an 18 hour retard. Here's the formula, I welcome any suggestions/advice.

315 g H2O room temp

162 g whole wheat flour

288 g artisan bread flour (central milling co.)

175 g ripe levain (mine was started off my mother at a 1/10/10 seed rate

12 g salt

Soaker:

50 g bran

50 g flax seed meal 

150 H20 (boiling)

1 g salt

Method:

Make soaker first by boiling water and adding 150g boiling water to bran/flax/salt mixture.

Dissolve levain in 315 g h20 with silicone spatula or by hand, add flours, mix and let rest for 30 minutes.

Add soaker and wait 30 more minutes for a total autolyze time of 1 hour.

Add salt, mix to combine.

In-bowl stretch and fold four sides to center and repeat every 30 min for a total of 5 stretch and folds over 2 1/2 hours.

Bulk rise for another 1 1/2 hours with no stretch n folds.

Remove from bowl onto floured work surface and preshape into round, cover with the bowl and bench rest for 30 minutes. Remove bowl and shape into round or batard, place seam side up in basket with liner dusted with rice flour.

Place in refrigerator with plastic bag covering the basket to keep dough from developing a skin. Retard 18 hours.

Bake cold from fridge: dust bottom with cornmeal, upend into cast iron dutch oven, score with razor, bake covered at 500 for 10 min, uncover, reduce to 450 for 10 minutes more, then reduce to 400 and bake for 15 minutes more. Remove and cool on wire rack for 2 hours before slicing. Enjoy!