Spark jumps from sharper corners much better than rounded, I have always filed my plugs by flattening the bottom of the strap, then taper each edge and the end into a paramid so the bottom edges by the electrode have the sharp corners. Bend the strap so the end of it is center of the electrode, not going past it. I have been doing this for 30 plus years and have never had problems with fouling, skipping plugs.
Also through experimenting with chain saws when I was a teen working in the woods and on snowmobiles, dirt bikes etc. I would take the plug out, change the gap, and retry in the hard wood over and over and over trying many different gap settings and always found more power by going to a smaller gap then recommended. Gapping larger always lost power.
From My back yard experiments.

55 Vicky & customline
58 Rack Dump, 55 F350 yard truck, 57 F100
59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?