The 5.5 SL number is with a jib. The mains should be almost exactly the same size and the mast hight should be very much the same...I did forget about the boomless main of the 5.5 however so disregard, it won't work unless you want to remove that track off your old main and add it to the F18 main. I used to have a 5.5 but forgot about no boom.

The Cape Cod Frosty is a very small homebuilt boat, looks like an Opti but SMALLER! There is a fleet (or used to be, when I lived up there) that races in the Portsmouth Harbor on Saturdays all winter...thus the Frosty name. One of the guys who was very into the Cape Cod Frosty racing also lived in Northfield and raced on a small lake up there. I went and raced one once...I barely fit in the boat and I'm only 5'9"!

I grew up in Hampton, went to UNH and flew KC 135's for the NH Air Guard for 8 years, we covered the entire state. Not too hard to do at 500mph. I've driven through Northfield many a time.