IBU/SG ratio for a stout?

hey guys, i am making a 3 gallon batch of imperial oatmeal stout, i am looking at an est. 11% ABV.... right now all i have is a one time bittering of hops at the beginning of the 90 minute boil with 1 oz of chinook... this puts me at 46 IBU's and a IBU/SG ratio or .444....

as i understand it, the ratio of IBU/SG is more important then the IBU number by itself. i figured 46 was a little high but the ratio seems about right for taste. plus i don't mind if its a bit hopped out

this is my first stout so just looking for some feedback: thanks guy!

i reassessed my hops & decided to go with 1oz of EKG & 1oz of cascade at the beginning of the boil. felt it might pair better with the stout..... that puts me at 42 IBU's & .401 IBU/SG ratio

Here is a good reference about BU:GU ratios.
List all different styles and the averages.

https://docs.google.com/spreadsheet/lv?key=0Ai1Yv492QZYUdFN1YWpYZTFxUm1reWN2WEx2a0xpUkE

awesome! thank you