Thanks again for all of your information RAH, Yeah I do wish I had more as it would seem an obvious benefit.
I found this information -
"A guide for estimating the approximate size of a drainage area (in acres) required for each acre-foot of storage in
an embankment or excavated pond"

on page 21 (Illustration 11) in this document - http://www.aces.edu/dept/fisheries/aquaculture/docs/AgHandbook.pdf

If I read that correctly it shows a broad swath of Indiana in a 3-5 suggested ratio. But I am also sure that I have read that suggested rations are much higher as you suggest.
Reconsidering my previous runoff perimeter at best I still only have 4-5:1 Looking forward to talking with my contractor again soon.

I don't know if you are still following sprkplug but I wonder what your ratio may be as I am just about 25 miles or so east of you.