I have now installed the "fitted" inwales around the sheer. These parts are steam bent around the sheer, are notched around the frame heads, and are a real challenge to build this way. They serve the purpose of strengthening the sheer, and indeed joining the frames to one another. When done this way (with notches) it also provides a nice spot to perch when "hiking-out". With the inwales installed, the hull is noticeably stiffer.
Though the notching was difficult, I think it may be a superior way to make an inwale, because it protects the end grain of the frame heads from the weather. The next step will be the breasthook and quarter knees.