Not quite sure where you're getting that 6-1. Based on a $266 Will Pay and a $43.60 leg 1 winner, after adjusting for takeout that works out to around 4-1.

I think I posted the takeout-adjusted formula on the board somewhere before, but for reference here's what it boils down to at NYRA tracks:

Expected $2 Payout = 1.73 x ($2 Will Pay / Leg 1 Winner $2 Payout)

In this case it's 1.73 x $267/$43.60 = $10.60, or ~ 4-1.

This isn't the best way to calculate it anyway though, for a couple of reasons. One, you don't want to just look at the single winner's payout from the previous leg, because if that horse's win odds were out of alignment with the Will Pays, it will throw off every horse's odds in the next leg. And two, you want to avoid using longshot winners in the prior leg because they're often overbet, relatively speaking, in the doubles, which will also throw off the estimates.

I use the first few favorites from the prior leg and the entire matrix of double payouts, rather than just the "quick 'n dirty" method posted above, to get the best estimates.

In the case of the Suburban, Preservationist was 3.3-1, 3.6-1 and 3.7-1 with the first three favorites from the prior leg, respectively.