I have twin 7 month old boys and they both wake up once during the night as well.
I too put them down between 7:30pm and 8:30 pm. I have tried putting them later but it makes no difference.
I am debating on letting them CIO but I think this time is so short, I will just put up with it and hope they will one day sleep through the night like my son did.
I have to tell you my one little guy can fall asleep on his own for naps and bedtime and the other needs to be fed to fall asleep.
They both wake up crying in the night and this seems to make no difference at all.
My Mom suggested feeding them later like at 11pm and see if they can go until morning.
I may try this on the weekend and I will let you know how I make out.
Good Luck and I definately feel your pain.....double!!!