:When I look down the length of the boat from the stern, it appears that the middle of
: the boat bows out the left. I can easily correct this by lightly
: moving the gunwale tips Should I go ahead and put the keel in place and
: position the gunwales and chine to the bow/stern plates in such
: a way that it straightens out?

That's a pretty regular occurrence. And your fix is as you suggest. But, first make sure that each pair of stringers, and your gunwales, are exactly the same length when you attach them. And, take measurements from the same spot on the bow to each side of your frames - and make sure they are equal on both sides - it's easy to get them twisted a bit, which is likely what is causing your bow.
You can/should also check for twist - here's a quick tutorial from CLC: http://www.clcboats.com/shoptips/stitch_glue/checking_twist.html

Good luck!