After marking the rib blank length (I went with the theoretical calculation of 1.687
instead of the empirical 1.677 value...we'll see if my flanges end up a bit to wide),
I drilled 1/4" holes for bend relief at the intersection of two flanges.
Then snipped and filed the corners out and edge deburred all but the diagonal edge. Actually
I did those edges just a bit as well...to make the parts easier to handle. I'll have to
re-cut that diagonal once I have the ribs fitted.