When installing the deck on my S&G Chesapeake, I used a router to painlessly trim the deck overhang. Using a straight router bit with a bearing on the bottom, I could get quite close to the side panels without having to worry about cutting into them (i.e., as with a saber saw). A low angle block plane made quick work of the final bit of overhang.

I also used the router and a "round over" bit to put a nice, rounded edge on the inner and outer lip of the upper coaming ring.

(I don't own a router, but was lucky enough to have a friend willing to loan me his relatively cheap Sears router. It wasn't fancy or super powerful, but it was adequate for my needs on this project. FWIW, if you haven't used one before, practice on some scrap wood first.)