The first two ribs need modified so the root carry though gussets and brackets can be installed.
The #1 rib at the rear spar looks like this.
At the front spar.
The root rib was a little more difficult to cut out since it is laminated with plywood.
The slots for the brackets looks good.
When assembled everything for together well.
Now that all the main ribs are completed I can start assembly of the right wing.