Plans call for two seat ribs s to have their lightening holes enlarged and their tops cut off to facilitate installation of the control sticks. But most builders are doing the modification to four seat ribs because it allows for assembly of the control sticks on the bench prior to installation. I like this idea so I'm cutting four seat ribs per drawing 22.
I used a 1 1/2 hole saw or bit with a center drill to first cut the hole. Aluminum is pretty soft like wood and I haven't had any problem using wood cutters on aluminum.
