I have a 4 door and in the developing stages of making my own kayak rack. Here is the back so far. Again this is super rough product and no where near finished.

 

I picked up a harbor freight trailer for this same reason. I did some searching and found a pic of what I want my end result to resemble

 

Over the weekend there was a new development in the kayak hauling situation. My uncle had a hitch mount T bar laying around in his garage that he gave to me. It's pretty similar to the one above minus that final bend before the top of the T. Now I just need to secure them to the front and we may be in business.

 

I can't help you with the top on however, are you ever going to go kayaking in the rain? But then I guess if you are going on a weekend trip, having the top on would be nice. Here is what I did for the top off.

I got an old piece of frame and cut "L" Brackets. (or buying L brackets will work too)
I then cut a length if rigid pipe to the width of my roll bars.
I welded the parts together
I then drilled holes for the screw to go through and Bazinga, you have a roll bar you can take off and put on.

You can see, it does sit above the windshield and the rest of what ever you are carrying will rest on the roll bar in the center.

Mine is only inches over the windshield, of course you can modify how you wish.