Could you confirm that it is possible to use up to 20% wholewheat flour in a sourdough recipe without any negative effects and does this 20% include the wholewheat in the poolish starter.
From your 70% Hydration Sourdough boule recipe:
Total flour content including starter =750g
Therefore 20% Wholewheat would be 150g but the total wholewheat flour in your Sourdough boule recipe is 225g (inc starter) giving a figure of 30%
Have I got this right please?