Guys, I have done the trip that you are talking about many times on my larger boat, (30ft Pearson). If you leave from Old Saybrook, or anywhere west of that you should be fine in reguards to the race (Fishers island to Plum island) Which can be hairy enough in a larger boat. Plum gut on the otherhand is about 300 yards of pure hell in a 16ft boat if you go though during max ebb or flow. It can be quite nice at exactly the tide change though. I would reccommend getting there 30mins prior to high tide. Either way, stay about 100 ft to the east of the light house and that will be the shortest and easiest route through.
I'd go myself if I had a hooter or a spin on my 5.0 but I think I'd be left in your dust (or spray!)

Have fun!

-Jeff