importance of aft bulkhead design in a cold molded hull

As per the title, Ive got a boat that is 30 plus years old but lacks a bulkhead or hanging knees at the aft end of the cabin. great access to the 1/4 berths but cant help but think it may be a cause for a bit of wracking. Any thoughts on the subject? I dont want to but looks like I may need to put in a substantial main beam and attach some 1/2 bulkheads to it. the boat is 10.5 metres by 3 metres by about 5 tons.

 

Is there any structural indication that the boat is racking (i.e. twisting or being pulled tortured on a rack as opposed to wrack which is ship wreckage/debris washed up on a beach...YMMV)? Any indication of delamination? Cold molded hulls are generally designed to be monocoque construction with reinforcement to prevent springing loss of geometry and to spread concentrated loads. Adding structure when no lack of strength or stiffness is apparent may actually cause a stress concentration which can lead to other failures. If you know who the designer/builder is, talk to them first. There may be a reason no bulkheads were needed or installed.