German Brewing

A few things off the top of my head:

You'll need more sauergut than that. At 0.8% acidity, you need 60 ml per kg of malt in your grist for every 0.1 pH you want to drop. For 5 kg of malt, to drop the pH by 0.4 you'd need 60 * 5 * 4 = 1200 ml. That's not counting for your end of boil addition either, if you want to do one of those (which you should). In the boil it takes half as much sauergut to drop by pH 0.1 (i.e. 30 ml per kg of malt in your grain bill)

My experience is that lodo wort doesn't stay "fresh tasting" when stored for very long, and sauergut stays "fresh tasting" for maybe 2-3 weeks in the fridge. I've found, however, that sauergut stays quite fresh when frozen. So I've been making my sauergut right after a brew, and after 24 hours I chill it and freeze it.

Sauergut is best made with unboiled wort. Just do a mashout at 170 F, draw off your wort, cool it to 118 F, then sour it. The wort you reserve for making yeast starters, however, should be boiled enough to achieve a good hot break because if the break materials aren't precipitated they can inhibit nutrient uptake by the yeast.

Thank you for the reply. I will change the approach to include more sauergut and will use it in the boil.

And just to confirm, I can a noticeable difference in the flavor of the beer when using sauergut made with fresh, unboiled wort and then frozen vs. using sauergut made a day or two before brew day with wort that was pressure canned? In my mind, the sauergut is replacing plain water, so I hadn't much considered the importance of the subtleties of its flavor. Surely, the lacto flavor contributions will come through either way, right?