My battens have now been ripped and fit to the frames. I had to deepen the pre-cut notches to get the battens to lay flush with the frame contours. Per the "Boatbuilding with Plywood" book, battens should be installed after side planking, so I used some steel screws for temporary dry fit so they can be removed if in the way for subsequent work. They helped secure the frames in position so I'll leave them in place if possible.
The sides of the middle frame were unsupported and could easily be pushed out of plumb so I added a temporary cross beam and some angle braces from it to the form to stablize them. Now they can be worked on without moving around.
The next step is fitting the chines. You can see in the photo that I'm experimenting with a piece of pine to judge whether my notches are right. I'm letting my buddy Ted forge ahead with his Zip and of course he just tried steaming his chines and installing and broke one. I'm taking a vacation so the boat will be on hold for awhile. Maybe when I get back, Ted will tell me how to install a chine without making expensive mohogany firewood.