....The crazy thing is that our friends at Chrysler have designed the roof bars so that my Tule cross bars can only be a max distance of three feet front to back. Supporting three feet apart seems kind a short on a sixteen foot hull shold I be concerned?
Car to beach is also undecided for me, plug in cart vs strap on, love to hear your advice.
You're right, three feet is tight, but we take our AI and Revolution on our Honda Civic with Yakima bars, and they have to be set just 30 inches apart. The solution that we found was Yakima Mako Saddles. Instead of your boat taking the forces of the bumps, the saddles do as well. Then use a bow and stern line to keep the saddles from flexing so much. It's very important to remember that the bow and stern lines are just there to keep the boat from bouncing too much on the suspension like saddles. They should be snug, but NOT tight. That's what will cause the boat to fail. The saddles actually work VERY well as a suspension to keep the forces of the road from getting to the kayak. By creating a gentle ride for the kayak, the boat is much less likely to face a problem. I do think that these boats are tougher then some people say, but it's important to follow Hobie's guidelines for storage and transport. Technically they recommend that the AI is transported on it's side or upside down, but given my 30 inch situation, by far the most gentle ride for the boat is with the Mako saddles.
As for your second question, I used to have a strap on cart for my traditional kayak, while my wife would use the plug in cart for her Revolution. The straps are time consuming and a pain in the butt compared to the plug in carts! When I bought the AI, there was no question which cart was the best for me. The plug in cart is the way to go in my opinion. I chose the Heavy Duty cart, but there are pro's and con's to each. I wish that I had beach wheels to make it easier to roll the cart on the beach, but at the same time, I almost always insert my wheels while still on the water, and it would be nearly impossible to push the beach wheels under the boat while sailing, so the HD wheels are a good compromise of being able to roll over almost anything, but still be relatively easily pushed under the boat.
Finally, when it comes to loading your boat on the roof, there are a number of posts by Roadrunner and others which talk about loading a tandem island onto a pickup truck with raised racks. There used to be a video on YouTube of a guy loading an Adventure kayak onto a Subaru. I can't find it right now, but there are others who can help you with a technique. It's not impossible, and some have managed to make it look quite easy. When push comes to shove, I'm able to load my AI on the roof of my Civic without any help, simply by muscling the whole boat at one time. It's a heavy boat, but it's not unmanageable.
Hope that helps.