Originally Posted by meanwhile

Remember that your new bars have reach of their own before your get your hands on the hoods, the main riding position. So imagine your ideal flat bar position and try to position your hoods there. Do NOT be scared of a short stem! Do remember than a higher stem is easier to reach, so that is the equivalent of a shorter one!

In your shoes I'd look for a 60 or 70mm stem with a 17 degree angle (that's as extreme as road stems get - I'm assuming your bars aren't oversize, and so you can't use MTB stems). I'd start with it flipped up to raise the bars and then flip down if you wanted a more aggressive position later.