I liked the effect of the buttermilk powder. It is very subtle. A slight increase in volume, similar to using regular bakers grade dry milk with a very subtle buttery taste. It seems to soften the crumb slightly and move it slightly to the bready side. It is almost the same as BG dry milk with a slight twist. A twist to the better in my opinion. It should be great addition in your Sicilian style deep dish.
I am also noting that the bottom of the pie was darker with the same bake time. So I am experimenting with less stone warm up time, around the 16-18 minute mark. I use the 20 minute mark with dough without the addition of buttermilk powder, BG dry milk or dried whole egg powder. The addition of 2 minutes takes the stone from 600-625 degree mark to the 650-675 point. No doubt it makes a difference in the bake. I am also finding that with the stone temperature "right", I can increase the flame for the bake, at the insertion of the pie, to balance out the bake to my taste. This is the effect of the pizza baker upon the final outcome that we all come to understand with experience.
I am experimenting with the above mentioned ingredients to learn their effect upon the final result. This is something that has to be personally experienced to be able to produce a result that is that "cut above" that I am forging forward to produce. The above mentioned ingredients are just a small portion of options at our disposal as I am sure you understand. Tons of fun with a great reward at the end.
Good luck with your new oven, you will love it. I look forward to your pictures.