Both the Tern and Coho I built ended up with minor overhangs like you're experiencing. I simply used a putty knife to pry the hull outward slightly, then held it all in place by pulling strapping tape down from deck to hull. I ended up doing this every 6 inches or so along the entire perimeter, but once buttoned up this way, it was easy to tack-glue and finish as usual.

It looks like Nick did the same thing in building his S & G Night Heron - and has photos of the process posted on his site. (See link below)

I hope you haven't glued the seams so much already that you can't pry the hull out to match - 1/8 inch overhang isn't bad at all!

Rick