Thanks for the article, Larrin!
Regarding chamferring holes:
I ran a couple quick simulations using 1/8"x3/4" flat with a 3/16" hole, under bending. I then looked at chamfers and hole shape changes. The ellipse is obviously impractical unless waterjet/CNC*, but an interesting point of reference. All chamfers are at 45°; increasing the angle didn't change much.
Round hole, unchamfered: 100%
Round hole, chamfered 0.01": 99.8%
Round hole, chamfered 0.02": 90.4%
Round hole, chamfered 0.03": 93.4%
Elliptical hole, 1/4" long, unchamfered: 91.3%
Elliptical hole, chamfered 0.02": 84.3%
Slotted hole, 1/4" long, unchamfered: 92.7%
Slotted hole, chamfered 0.02": 80.2%
Increasing the length of the slot did not futher reduce stress.
Two overlapping holes had similar stress reduction to a smooth slot, at 90% unchamfered and 80% chamfered.
*A waterjet hole might have worse stress concentrations due to surface finish.