There are 3 bridges over the Harlow Canal with low clearance. Even capsized, you might not fit a catamaran under them. The canal is also narrow and closely wooded with lots of overhanging branches. I think unstepping the mast is pretty much mandatory.

That said, There is a place in the Clubfoot Creek near the canal entrance where one can pull up on shore (or at least duckgrass) and unstep the mast. There is another spot at the canal exit where one can put the mast back up. Watch out for oyster beds, though.

There is a drawbridge over Town Creek a little farther along the NCC. It normally opens on the hour and half hour but I think they raised it on demand for competitors last time. If necessary, one could capsize walk a boat under that bridge.

Regards,
Eric