: I have seen some sit on tops, and touring Kayaks that are short and wide.
: I would like to design my Kayak shorter, so that it's easier for me to
: transport. I cannot lodge a 17 footer on top of my car for sure!

Buy or build a trailer and you can tow a boat behind your vehicle. Small trailers even work with bicycles and motorcycles. With a trailer you can take along several boats, so go paddling with one or more friends.
Or, build a kayak which can be disassembled and carried inside your car. Many of Yost's designs can be built as 'folders'.

Also I
: just saw some Kayak shops online that sell less than 10'Kayaks that can
: take 350lbs. paddler.

Ummm, take those figures with a grain of salt, as the idiom goes. Don't confuse the maximum capacity of a boat with the displcement it was designed to work well at. A small boat may indeed be packed with a lot of weight, but it will be very deep in the water. That may not be safe.
An example: A 17-foot open canoe with sides 12 inches high is designed for two paddlers -- a weight of about 350 pounds-- with a draft of 4 inches (about 100 mm). The freeboard, or amount of the side of the boat above water would be about 8 inches. That same boat is rated to hold a maximum of 950 pounds. At the top weight the draft would be about 8 inches, and the freeboard about 4 inches. Any waves, or rocking of the boat, when loaded like this would cause water to splash inside.

: So it is a lot of encouragement for me, and now I
: know that smaller Kayaks can handle 200+ pounds.

So can inflated innertubes, and inflated liferafts. But they are not a lot of fun to paddle.

The cockpit should be large enough to allow you to get into the boat. In rough water or heavy waves it is easier to keep dry with a smaller cockpit and a tightly sealed spray skirt. In calmer conditions a large, open cockpit may be more comfortable.

See next note
PGJ

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