Well, it is starting to look like a usable canoe.
After the first round wrestle with with the 3mm ply and the compound deck curve I decided to clamp the deck during glue up with ropes tensioned directly over the deck beams. It was a bit of a struggle but seemed to work in the end.
The combing, on the other hand, proved a bit more difficult. Initially I had intended to glue laminated strips to build up the combing but three failed attempts taught me that the the bend radius at the front of the cockpit was too tight. Yes, I am a slow learner. Plan B was to layer ply segments around the cockpit rim and and fillet with epoxy. So far so good. Two 6mm layers and a wider 4mm cap have built up the basic shape. I now need to finesse the shape and apply a neat epoxy fillet.