Paul,
In America a 200 lb. person may be considered average but in the rest of the world he is big and he should probably paddle a good sized kayak. Length translates into carrying capacity so a 200 lb. paddler with 20-40 lb. of gear should load a 15-16 ft. boat nicely. Lenght also translates into speed which most people don't care about but they do care about glide which is better in longer boats.
I've never paddled the Hudson but I would catagorize it as "big water". It's more like a long narrow lake than a river. It's so wide that wind has plenty of opportunity to get at you. A full size sea kayak should work well there.
Home built boats can have any size cockpit but ready made spray skirts only come in certain sizes. A boat with an odd size cockpit has to have a custom made skirt and is at a disadvantage when it comes time to sell. A "super keyhole" is a fairly ample cockpit opening and folks much bigger than you use all the time. Kayaks are hard to get into. It's a fact of life. Even the most experienceed paddlers have a drill they use to get into their boats. Every one of us has paddled all day without a mishap only to fall in the water when we tried to get out.
The cockpit and whats below it should be snug but not tight. A snug, well-padded cockpit is comfortable and helps the paddler control his boat better.
Hope this helps.
Charlie

: Howdy,

: I am looking at building a kayak. This will my first attempt, but I feel
: comfortable after reading the reviews and recommendations here. It will
: mostly likely be a stitch and glue kit since they seem easier (and
: cheaper?) than other types.

: My question is about the size of the kayak to get. I have looked at various
: plastic models that are in the 12ft to 16ft range. The 16 footers seem
: quite big for me. My planned use is lakes and quiet rivers, like the mid
: Hudson Valley in New York. The Kits I have seen are mostly larger than the
: plastic models I have used. I understand that these are "Sea
: Kayaks" and will be bigger for use in the open water.

: The kits that I originally thought would be good for me were 14ft, but the
: descriptions state that they would be good for children or small women.
: Well, I am an average guy at 5-10 and 200 pounds.

: I am also concerned with the cockpit opening. Some of the plastic ones I have
: used have openings that seemed small, making it harder to get into. None
: of the descriptions I have read online state the cockpit opening
: dimensions. Is this something that can be adjusted during construction?

: I should add that the plastic models I have used and thought of buying were
: called recreational or day touring kayaks.

: Any thoughts about a "short" 14ft kayak for an averge size guy ?

: Thanks, Paul