The ply bottom has been replaced. Today I finish replacing the port chine board. After that on to the bottom planking! After much deliberation and consultation I have made the decision to use a new material that I am fairly sure has never been used on or in a restoration of such a boat.
The material is a vapor barrier manufactured by VaproShield. This membrane "A mechanically attached, water-resistive vapor permeable sheet membrane" has been tested to hold, without leaking, a 24" column of water for 48 hours. Basically, a much better membrane than the "waterproof" canvas that was originally installed. In addition to this reasoning it will allow the movement of water vapor through the layers of wood avoiding any pockets of moisture that will allow rot.
Another consideration is the ability to be repaired. With a 5200, West System or fiberglass bottom that are popular repair is a tedious and non-traditional process. The WallShield product is flexible can handle high heat (fire rated), tightens around fasteners, has zero VOC's, doesn't dry before being worked (like 5200 or BoatLife), is very affordable, is the closest to original construction, and (most importantly) it is tear resistant. In short, is does everything that the original water barrier meant to do.
I'll keep you updated on installation.
Off to work!!