Uke buzz

I know, been covered a zillion times. This is a vintage Favilla U2 sop, buzzes very slightly on G & more prominently on C. New Martin M600 strings. Buzzes open, or fretted, but only when strummed fairly hard . Not terrible, but there. The buzzing stops when I touch the soundboard, from the middle of the soundhole down to the bridge. Also stops when I touch the bridge. I'm thinking possibly a brace, but it didn't seem too dry, since no cracks or fret sprout. Any ideas, before I take to a tech? (or just live with it).

I saw your post also above in http://forum.ukuleleunderground.com/showthread.php?10546-Buzzing-on-String-Instruments-Causes-and-Cures
No reason to tolerate buzzes. I've learned they can come from just about anywhere. Last month I "fixed" an older gent's buzzing guitar by removing a pick he'd dropped inside.
I'd take it a good luthier. Let him/her check it out. It might be a simple fix, but then again, it might be a loose brace or some such thing you don't wanna mess with yourself.