I'm an American. I grew up in the Midwest. And I've always said "towards" and "backwards" and "frontwards" and all that sort of thing. And that's how I have those words in my almost-finished novel. But the grammar check facility in my word processing program tells me those forms are British and I should change them to "toward," "backward," and so on. And for awhile I was acquiescing. I don't want to disturb the reader. But now it just sounds too weird to me, and I'm thinking of putting those Ss back in. What do you think? Does it matter? None of my beta readers has noticed it, not even the one who thought I was using vocab over her head. My novel is set in the American Midwest, if that matters.