Cam Duration Vs. Usable/Used RPM Range

I have some other questions back at you...
What info is Crower using to determine those power ranges?
Do you feel that the time to determine the cam is after the rest of the package is put together?
What determines the "minimum amount of duration to achieve a rpm shift or redline"?

I think I know what you're asking - but the way you're asking it doesn't make much sense to me... if that makes sense...lol.