Kiz,

I didn't realize there was a rear deck beam on the Chesse's...?  Mine (17) had only the forward beam; however, I added another front and back to help maintain the deck curve when cutting out the hatches.  As to their curve, they should hold their shape.

Bulkheads have specific dimensions from the bow and stern; they're indicated in the plans.  Becomes an issue for your cockpit and foot room if you mis-place them (too far forward or aft).

Good luck,

Larry

Regarding the bulkheads and the forward deckbeam ... yes, there are measurements for where they are intended to be placed, or at least that was the case with my Ches. 14 and LT-17. They are found on the top view of the boat on page 1 of the plans, or at least that's where they were for both of my boats.

As Larry notes above, these boats don't have an aft deckbeam indicated on the plans, but I agree with him that adding them forward and aft to support the deck near the hatches is a good idea.

For the LT-17, which is similar in size to your 16, the forward bulkead is 61 3/8" aft of the bow, while the aft bulkhead is 121 1/4" aft of the bow.  The forward deckbeam's after edge is 89 1/2" aft of the bow. Your measurements should be similar, I imagine.

More important, the aft bulkhead is a little bit aft of the inside edge of the coaming, while the forward bulkhead is far enough forward to clear your feet. Consider the point Latty makes: the bulkheads define the length of the cockpit, and the cockpit need only be big enough to accommodate the paddler.  Anything more, and you're reducing your stowage in the forward and aft compartments, and increasing the weight of water that can come aboard if the cockpit floods. 

Are you building from plans? If so, I recommend making a cardboard mock-up and test fitting it. Many builders find that the plans for the bulkheads (the forward bulkhead, especially) are not accurate, but leave a substantial gap between the bulkhead and the deck, especially at the center.