DEVIG PROPS

How the math runs. Every leg's win probability comes from de-vigging a sharp two-way price — type the market both ways (say -140 / +115), the overround comes off with your chosen model, and the fair side probability is what feeds the slip. Nothing is hardcoded: the actual platform payout field is the multiplier the EV formula uses, so put in whatever your app is really offering for that slip size. EV per $1 = fair hit probability × your payout − 1. Power Play needs every leg. Flex Play uses the exact Poisson-binomial distribution over all hit counts, so partial payouts are priced properly rather than approximated. Book parlay multiplies your own decimal prices instead. The ladder scores every legal subset and sorts by EV — tap any row to switch the slip to it, and an amber multiplier means that size is running on a payout you typed.
The four models disagree, on purpose. Multiplicative is harshest on favorites, power is kindest, odds ratio and Shin land in between. On a two-sided prop Shin is mathematically the same as splitting the hold evenly. The EV floor reprices the whole slip using whichever model is least generous to each pick, so you can see the pessimistic case without switching models.
Assumptions worth knowing. Legs are treated as independent. Same-game props — a scorer's points and his team's total, two teammates' assists — are correlated, and correlation makes real Power Play odds worse and real Flex odds slightly better than shown. De-vig from the sharpest two-sided market you can find; a fair line is only as honest as the price behind it.