As far as I can tell one or two instances are enough for concern. My car exhibited no knock events at all on the dyno, no overheating etc. I was told on many occassions that streghtening the pistons to (forged) is only going to reveal other week points like the cylinder wall.
Was mine a one-off issue possible, but now that I know about it, there are more people coming out of the woodwork with the same issue.
Kapp I am in the same boat as you, I have a brand new 704 series SB is sitting on the floor was ready to go in and I stopped it. Going full build this time with an older series 702, lets see what happens.