OK, it's been a few weeks.  Had one of my flying buddies and his family over for dinner, and we went out to the garage to check out the project, and figured "why not drill those holes now?"  When will I learn!?  Both "mistakes" have been when I worked with spectators.  I (we) drilled out those holes, and despite the careful measuring a month ago, something went wrong...  as I held things and my friend drilled through with the angle drill using the carefully marked / measured / drilled pilot holes, the bit popped through to the front (the aft HS-404 flange) and I immediately knew there was a problem...

That hole was only 1 diameter from the edge of the piece.  Minimum edge distance is 2D from the edge of the metal to the center of the hole, or 1.5D from the edge of the piece to the edge of the hole.  This hole is only 1D from edge-to-edge.

Will that mean I need to replace HS-404 with a new piece?  Is this one okay?  Or can I "fix it" by adding another rivet in the middle?  I've got an email into Van's Support... we'll see what they say.  Some experienced builders I wrote to think the part is salvageable. 

I'm not in any hurry, this part is small, easily replaced if need be, and I've got plenty to do that is not dependent on the HS-404 being ready anytime soon.  I'll update this page when I get a definitive answer.

UPDATE 4/18/06: I got a reply from Van's Support... "I wouldn't worry abouth the ED on the rib, you could use a doubler over the flange if you want, but it's not necessary." Sounds like I get to keep building!