Easy Razz fold?

[Trencherman]

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Easy fold. If the Ace had raised behind you, then the pot would be big enough that you would have to take a card off. The pot is small, and while your hand was very pretty on third, your situation on fourth is pretty bad. It happens. Fold and move on.

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This is standard advice, but can you relate it more generally to pot size? For example, if the ace had raised on third, the pot on fourth would be 5.3 small bets. Are immediate odds of about 5:1 the absolute minimum for a fourth-street call when Villain catches good and Hero catches awful?