Grind size/ratio adjustments for small dose pour overs?

I made a pourover with a v60 today with only 10g of coffee and a 1:15 ratio. It was the same grind size, ratio, and roast as a coffee I made a few days prior, but that one was 20g of coffee. The larger pour over I felt was balanced, having some fruity and manageable acid flavor, but this one was sour and a little bitter (which would indicate over-extracted?). And at one point, the flow slowed to a crawl and I just stopped letting it drip at about 15g water left in the cone.

Does anyone have advice for smaller dose pour overs? How should I adjust the grind size and/or ratio compared to a more standard, larger dose pour?