It seems that this boat is equipped with oarlocks and oars. It is very easy to shorten any of these boats by just shortening the bottom and side pieces by the same amount. There seems to have been three different paths taken to overcome flat bottom wood boats limitations.
Flat bottom swamp boats
Attach chine log stubs on either side of the bottom. It depends. Or rather, attach the cross pieces to the underside of the frame bottom leg before installling the frame. A sensible frame to frame separation would be about 1'.
Where the mutual masturbation women will sit, install cross-wise pieces of the same material that You used for the chine logs. Some of the plywood is left over. Side on the side of the bottom. But that depends on the thickness of plywood, so some experimenting is needed.