65% hydration

Back to the usual recipe again. Turned out just fine!
100 g Swany 9-grains blend
100 g spelt flour
300 g Swany bread flour
125 g sourdough (50:50; some rye flour in the mix)
325 g water
Usual mix, rest, mix, 2.5 hour room temp ferment, shape in banneton, dough retard in fridge for 9 hours (I was in a hurry) and bake.

65% holds it's shape better than the 75% when out of the banneton but I'm still not getting slashing to do what I want. I slashed deep enough and the decorative shallow slashes came out great, but not the major slash. Looking for that perfect hydration to get the holey crumb and beautiful outside. I do like the long banneton better than the round for regular use bread. I wonder if the baking method is making a difference in the slash/rise rate? With the rounds I can use the dutch oven but with the longs I use the oven stones and on top a cast iron 2 burner griddle, preheated at 525 F for an hour with a pan at the bottom for steam. When the bread goes so does the water for the steam. Maybe not enough steam for that rapid oven spring???

Need to get another 25lbs of Swany Bread flour. Will stop at the mill on the way to Battle Lake this weekend.