Hi Mike and welcome to the forum.
As you may have gathered, the deck and superstructure was made to sit on the floor (carpet) and originally did not have a Hull.
A Hull was made for it later on using hardboard, covered in fibreglass below the waterline and using a single shaft.
There was a convenient lip on the underside around the underside deck edge, and the Hull was made to fit inside this lip. The weight held it quite securely in place.
I have more pictures at home on the laptop. If you pm me using the "message member" button and send me your e-mail address I can send some over.
Ashley