I built a 16 and would not recomend it.  If you are building from a kit the the deck panels may end up too narrow to make up the added width that would be needed to span the boat.  There is some overlap that is trimmed off, but it is hard to know how much extra you will have.  The front deck bends in 2 directions since it spans the cockpit widthwise with a radius, then is bent up legthwise a bit at the rise of the bow.  The more you ask the plywood to bend, the harder it is to get it correct.  You would also end up with a tall boat for it's size with strange looks and increased wind resistance, already an issue with this model in a cross wind.  The 16 is already a fairly wide and tall boat for it's length, and if you think you need more room, build the 17.

I'm a little late in my response, but why not just remove the deck beam altogether once the deck is in place?

The Arctic Hawk doesn't have a deck beam (in the front of the cockpit) as far as I remember, and it's not really necessary on most of the CLC designs.  Yes, it provides some strength and stability but that can be partially replaced with glass and it is already overdesigned.

I removed the foreward cockpit deck beam from my NorthBay when I built it and have never had any problems with it.  I just added an extra layer of glass underneath the deck for about 2-3 feet in the cockpit and the deck is plenty rigid for me to sit on (I weigh 165 pounds) without any issues. 

Changing the radius will change the shape of the deck, which will mostly be an aesthetic change rather than a performance change.  It could change some of your performance in windy conditions, but I wouldn't expect it to be very drastic with slight changes.  If say you change from a 16 to an 18 radius (I don't know the actual deck radius of the Chessies) it would make some difference in wind load, but as Steele already mentioned the Chessies are prone to wind already.

I guess my confusion is whether you're looking for more volume or more space for legs.  Changing the radius could give you more volume, but if you just want more volume, there are other boat options that would be better suited than modifying the Ch16.  If you're looking for "comfort" space, then modifying is always doable and generally doesn't have a major impact on the boat's performance.

FrankP

Forgot to mention the bulkhead... move it hwere you want or build a new one if you want to move so far that it affects the hull shape.  Each of these boats is individual and the positioning of the bulkheads is a guideline at best.  I'm currently in the process of putting a new deck on my boat and I'm moving the foreward bulkhead 6 inches further to the aft.  If you want more storage space, use the bulkhead in the position it is designed for as a temporary bulkhead and make a new bulkhead for the position you want it to actually be at permanently.

FrankP

Forgot to mention the bulkhead... move it hwere you want or build a new one if you want to move so far that it affects the hull shape.  Each of these boats is individual and the positioning of the bulkheads is a guideline at best.  I'm currently in the process of putting a new deck on my boat and I'm moving the foreward bulkhead 6 inches further to the aft.  (I already moved it aft during the original build by about 3 inches... way too much cockpit space designed into this boat.)   If you want more storage space, use the bulkhead in the position it is designed for as a temporary bulkhead and make a new bulkhead for the position you want it to actually be at permanently.

FrankP

Forgot to mention the bulkhead... move it hwere you want or build a new one if you want to move so far that it affects the hull shape.  Each of these boats is individual and the positioning of the bulkheads is a guideline at best.  I'm currently in the process of putting a new deck on my boat and I'm moving the foreward bulkhead 6 inches further to the aft.  (I already moved it aft during the original build by about 3 inches... way too much cockpit space designed into this boat.)   If you want more storage space, use the bulkhead in the position it is designed for as a temporary bulkhead and make a new bulkhead for the position you want it to actually be at permanently.

FrankP