[binions]

I don't think DIPO works that way when you are trying to figure runner runner. DIPO is usually applied trying to figure outs for the next card.

Put another way, you need 23.5:1 under DIPO to see both cards, not just the turn.

So really, you should divide 1.91 by 2 to get 0.96 outs for a backdoor flush draw. This is accurate. I have rounded to 1.