Surfskis and Outrigger Canoes are relatively long boats to transport with car roof boat racks and carriers. If you haul such long boats on a sedan or other short roofed vehicle, there will be a lot of boat not supported or controlled by anything longitudinally unless you add longer supports to your roof racks. Such racks can be home made with a little ingenuity or purchased from several manufacturers. Longitudinal support can also be increased for some cars via a trailer hitch mount.
several of these have the option of removable V ends which can be quite valuable if you anticipate needing to park in parking garages or anywhere else with low overhead clearance. Some of them sometimes do custom work or offer extension options that are not necessarily obvious or even shown on their websites. If you are thinking about a change/improvement/variation or something you do not see in one of these base designs - ask if they can help you get what you are looking for.
Note that carrying your boats at an angle (video link) may decrease the stress from cross wind but it can also increase lift making the strapping suggestions even more critical. One of the ultra light surfski manufacturers, Nordic Kayak, recommends the angled approach for their surfskis in V racks. Owners of other very light boats, including most OCs of recent vintage, may also want to seriously consider this carrying position with V racks.
You want to keep your boat and equipment clean and dry. Rinsing with fresh water is particularly important after each outing in salt water.
Boat covers can protect boats from UV during outside storage (the cover itself will decay instead) and they can prevent dings from flying rocks, etc. while traveling. But JD Davies in the Gorge reports that covers with any slack in fit will flap against boats while driving on highways and dull boat finishes.