:I also made a Putz Walrus more or less acording to plans. I did modify the cockpit area by using eighth inch plywood sheets instead of the cross bracing trusses suggested. The floor was installed as usual. I found my boat very tippy.
Since my lower back is not strong. I felt I had to lower the floor in order to get a useful boat that I could paddle for a longer time.
I took out the floor timber that was in the middle of my seating area. Then I lowered the floor in the two sections where I sat by fitting two sections of eighth inch plywood one at a time into the now two sections. I had first spread the bottom with a temporary rib before I chisled out the floor timber so that the stretched nylon skin would not contract and reshape the boat. That is why I had to put the floor in two separate sections. one to the temporary rib and then when the fiberglass was dry.I put in the second section. The floor was screwed to the keelson and bilge stingers and to a piece of wood I had butted to the chine. The plywood was first fitted into the area with many adjustments. Then I glassed the bottom and waited until the glass got sticky then I screwed it down with with I think it was half inch brass screws (It might have been three quarters)After both sections were in and dry(take out the rib after the first section is dry and fit the second section to the first section. One section of floor will hold the shape of the boat) I then fiberglassed the top of the floor and since I had already modified the cockpit area previously I could also put fiberglass up the sides for added strength.
I could have left it like that and just slipped my feet in over nylon but I decided that that might be risky so I left the next two floor timbers in place and also put in plywood floors between them in the same manner. I now had four sections of floor all the way from the back of the cockpit to where my feet ended. The boat is a lot more stable now since the floor bottom is only three eighths of an inch above the nylon. there may be some problems with this design such as the inability to get out sand or small rocks if they get under the floor. They could abraid the nylon (but I launch from a dock). Lots of luck if you try similar modifications.
My boat seems strong and ok on the lake where I live but I don't go out in waves more than about one to two feet high.
Has anyone else tried modifications like these, Mike?