Anyone using cohumulone bittering formula with AA%?

I am starting the process of tweaking a rye porter recipe I brewed a couple years back. That beer was a big hit, but the bittering hop was Cluster which added a taste not unlike sucking on a tin can. I know its the Cluster because I brewed the Smashing Pumpkin Ale and had the same experience. So I want to change that. I grow Nugget and want to make that substitution, but there are other differences. Doing some research, it sounds like Cluster’s high cohumulone % enhances it’s bitterness which might be what I interpret as that tin can taste. Just a guess. Nugget is higher AA%, and if I took an average guess on AA% on both these hops, I would add 0.66oz of Nugget to replace the AA Cluster would give the beer.

 BUT, I found a cohumulone bittering formula on The Homebrew Hedonist website looking at AA Bittering Power:  AA% x(1+cohumulone%/2).  So basically, the number is higher than the AA, but high cohumulone varieties have an even greater difference between AA% and AA Bittering Power

  If I use this formula on both of these hops (Cluster being high and Nugget being low average) as a comparison, then I would add 0.70oz of Nugget to replace the same cohumulone that Cluster added.  Granted this is not a huge difference, and obviously I would go with the 0.66oz because I don't want the same perception of bitterness that cluster added.  So I can say I have the same AA%, but I can be a bit more certain that the perception of that bitterness will be less and therefore smoother in this beer.  Hopefully my hops have an average AA%, and yes, I know homegrown bittering hops is a crapshoot, but I have succeeded with my homegrown bittering hops before.  Has anyone looked at this formula as well as just an AA%?  Do the softwares ever consider more than just AA% when comparing hops for substitutions?  Does these softwares have a database of hop stats already loaded in them to guide us in our substitutions, or do we have to plug all that in?

 Also, I am going from extract to AG and pellets to whole hops.  So would it be correct to add 25% less due to AG and 10% more due to whole hops?  In other words, 0.66 x 0.75 x1.1 = 0.55?