Spirit run abv question

[rbsc]

Promise I’ve searched and can’t find this. I know not to put more than 40% abv in the boiler, but my question is does diluting down really low, like maybe less that 20%, harm the final product? I was planning two ferments of ten gallons. Thought that was a good volume. But now I’m reading to expect about four gallons at 20% from that. I need to end up with six gallons to safely cover both internal heating elements (one will end up turned off so maybe I’m being overly conservative here). Would have thought two ten gallon mashes would be plenty to start but unless it’s ok to dilute way, way low maybe I need to save up even more than that? TIA.