Fixing Ribs

At this point you have made a pair of slightly modified
side panels, that have a curved chine edge.

At each layout line on the side panel you should
have written down the distance you remvoved by
cutting to the line. In other words, at the middle
temporary rib, if the pencil line was 4" up from the chine
edge, then measure 4" up from the chine corner of the temporary
rib, along its outside edge.

Mark that 4" spot on each side of the rib. Connect the
two points left-to right. You now have a pencil line going
from side to side along the bottom cord of the rib.
If you cut that much off the bottom of that rib, it will now fit exactly to the
modified side panel. Do that for each rib station.

This can be a bit tricky to visualize. But it works. By curving the chine and by chopping a bit off the bottom chord of each temporary rib station, you've altered the bottom profile of the boat. You've gracefully lopped 4" off the boat's original rocker profile. Now follow the assembly instructions without change.
You will end up with a boat that has a flatter
bottom profile.