When using the template to set the rib I found it easier to drill both channels and drill at the same time. It does take a little set up time but seams to maske sure it all lines up. I did use a straight edge along both braces together to line the channels up which helped with the alignment. The l-angle they suggest to use, is perfect to line the channels up. I used cleco clamps to secure.
Template to set rear channels
Channel clamped to rib. I used a baker on the alternate side of the rib.
