Back handspring, hands basically lined up (opposite hand to starting foot in front preferably), second hand can be turned out. Hands the same as handstand/walkover NOT an acceptable choice.
It's pretty awkward. Possible, but I would discourage that hand placement on walkovers. The slower speed also seems to lend itself to crookedness with that hand position. I've seen a lot of girls start doing it (not intentionally) and it doesn't really work out, just like you wouldn't teach cross handstand that way (though working handstands with back handspring hands as well when they get to that point is good too).
It's a deduction at L6, and when you first start to learn BWOs, staggering your hands makes most girls go crooked. However, I've seen optionals revert to BHS hand placement on BWOs, and I think the end result really depends on their flexibility and control.