Jerry, I don't think I'll bother trimming the top of the pistons. I'm pretty confident there won't be any interference.
Otto, No idea why that notch was selected. It's been that way for years. These pistons have an expansion cut on one side of the skirt (the one that gets less pressure - opposite the side that gets forced against the cylinder wall on the compression stroke.) Some pistons have offset pins for a similar reason. You'd have to ask the piston manufacturer for a real answer.
