I meant W-4, but since you recieve W-2's in the mail, I remembered that # first
I changed mine years ago to withhold a lot from my check, when I was in self-business, as I owed a few grand each year. Since I have stopped doint that I never went back and re-adjusted. So the short answer is I will get more in my paycheck by adjusting my W4, less in April, and will not affect my Hybrid credit at all.
I now see it seems to be tied to income, income = tax due, nothing to do with tax withheld.