Cartopping an 18' boat ? Wow.
It isn't about the length so much. I have built an aluminum rack that supports them well. The are all either Kevlar or graphite so they don't weigh much. The new Pro boat is all carbon, 18' 6" long, 27" wide at the 3" wl and weighs just 31 pounds. Not a serious strain. The heaviest boat is about 50#. The Admiral usually helps me load that one now. Ha!
And of course, since we still have geese at the airports...you know, just keep looking over your shoulder for inbound aircraft. (G)
You never know, do you?
Everything inside the bulkhead line (end of piers) is private on the Hudson side of NYC, but the folks at the Intrepid Musuem never used to mind folks ducking in to admire the ships up close. FWIW.
We have no plans to stop but likely will find some of the stuff along there deserves scrutiny.
I grew up down that way on the Croton River and used to ply the waters of Haverstraw Bay as a kid. It looks much smaller now.