Straddling the foul line

[Manny A]

I honestly see no benefit for U1 to straddle. Does it really buy you that much of a better look at a checked swing? I seriously doubt it. And you could actually make it harder to see a tag on a pickoff when the runner dives to the back side of the bag, since the runner will screen your view of the tag. Most pro U1s I've seen actually set up a little bit off the line, further into foul territory.

As for U3, I can see where he may want to set up straddling or even into fair territory just slightly. I personally wouldn't do it. I can usually see around a runner at third for the check swing, and take the quick step to see the pickoff at third.