I was looking at an old post on cartopping with factory roof racks where the laser actually pulled the roof rack off the roof (not a Dodge) with destruction of the Laser. Anyone have any experience with carrying a Laser on a Minvian?
I used to car top my Laser, on a Toyota Sienna in the US and on a Renault Kangoo back in Europe, both with factory racks. Never had any problem. (Other than it is a pain to get the boat on and off the roof, but I guess that's another topic, I ended up using a trailer)
If you are concerned about the strength of the roofracks, don't rely just on tying the boat to the roof rack, try to spread as much of the load holding the boat to the van as possible to the van itself rather than to the roofracks. Have a line going from the bow to the front bumper or frame of the minivan which should help keep it from flipping backwards. If you can engineer it, a line from the back of the boat to the rear of the van might also be a good idea.
I've had a '97 and '98 Caravan. The roof rails are fine, but the thin aero crossbars are pretty worthless. I have Thule bars, with quick connects to attach them. I always strap down to the rails, not just to the crossbars.
I remove the crossbars when not in use to restore aerodynamic efficiency.
Most factory racks aren't rigid enough to support the weight of the boat (in my opinion). I've seen many people place foam padding between the boat and the roof of the vehicle. If you really don't want to get Thule racks, I think this is a better option than relying on factory racks alone.
You can cartop a laser with most cars as long as you make sure its tied/strapped down well. Make sure that the roof rack is solid. I used to car top my laser down to the water frequently and found that a good set of crank down straps will hold the boat down very well. Some roof racks will mark the deck or even damage it so make sure you cover up any protruding clips and hooks on your roof.
That being said, about 2 months ago a brand new laser fell off on the highway shattering to bits and causing a massive traffic jam. It is essential that the hull be tied down securely and remember there is a laser on your roof so don't drive like a maniac. If you are worried about using your car find a friend with a pickup truck.