There was a time when you could say that shorter pins rolled earlier, longer pins later. Now, with todays strong cores and covers, the pin length is almost negligible. Longer pins are usually drilled with the pin higher above the midline, giving length. Shorter pins are usually drilled with the pin closer to the midline, giving earlier roll. That's about the most effect you'll get out of pin length.
2-4" pins give the most flexibility when choosing a layout. Especially with 2-3oz of top weight, you can put a shorter pin higher and a longer pin lower and still be able to get the ball legal.
I would say you're correct about the blems. Shorter than 1" and longer than 5" I'd call a 2nd, blem, or pro-pin (the latter is usually only for longer pins).
I'd say 2-3oz of starting top weight is the most flexible. Even large CG swings or exceptionally high or low placement will not result in a ball that can't be made legal.
SH
