Hi, I increased my Ch 17 cockpit by 4" and moved the bracing by 4" without any problems. I used the kayak all last summer and she handled great. I do not know how large you can increase the cockpit without effecting the stability.

I am making my CH18 cockpit bigger --- Hey you don't buy an '18 if you will fit in a small cockpit :)

I am using the existing cutout as a template, and what I have done was to add 1 1/2" in the front, 4" in each side and 3" in the back.  

this stretches out the cockpit to 20" x 35" - which is just big enough.  

I will be measuring out and moving the deck beam about 5" forward to accomodate the larger opening. 

Here's the WD12 cockpit coaming overlaid on top of a CH16LT. According to the plans, the dimensions are very similar to the 17LT. The WD coaming slops over the deckbeam and bulkhead, but not by much. It should be quite possible to move both to stretch the cockpit and it should just fit on the sides. For that matter, Lee, a very active poster from the early 2000's, used to advocate the complete removal of the deck beams after the deck was attached to the hull. This was to save weight.

If you did end up using a standard WD coaming assembly, you'd be able to use the WD cockpit covers and spray skirts.

Laszlo

My only additional comment is that your posterior needs to land in the same place with respect to the hull.  You probably want to add most if not all of the stretch to the front and only a little to the back so as not to shift your center of gravity.  A stern or bow heavy boat will not track well.

Ed