It rests on the chine and the keelson, so the angle of the notch is correct, even on the forward frames. I have to be careful not to lean on is or it will bend, but in practice that has not been a problem. There was a little tearout, but this is a boat, not an Heirloom Cabinet.
The first side went quite slowly, much of that was due to constantly measuring the notch I had just cut to make sure it fit perfectly. The second side should go more quickly.
The two battens, running fore and aft in the picture, that limit the movement of the router are 2 1/4 inches - the diameter of the router bit apart, this leaves a little wiggle room.
On the first side, I had hand cut the notches for the center batten, so I left the center batten in place to leave me with a shorter gap to bridge with the jig. Less flexing.
You may notice that this Jig is essentially the piece of ply I used to cut the slot for the centerboard as previously seen here