More overlap allows a better cyl fill which means more cyl pressure allowing more power, up to a point in which reversion would cause more issues and loss of power. Also depending on the combo/port design less overlap would make more power since the ports allow for better cylinder filling with less overlap needed, so having more overlap would cause those reversion issues sooner.
I think that might be correct.. most of it was in the video i posted above though.. There is soo much stuff to cam selection that it's turning into black magic for me.. for my 318 using vizards method i come out with a 109 LSA.. that's bout all i've come up with so far.