I usually try to push to around a 1:1 BUGU ratio... I've got a Rye Double IPA that'll be around 150IBU's, but I know a lot of those will be lost in solution. I wouldn't be afraid to push 120 with what you've got, but then again, it's whatever you're going for. At around 90 though, there's a good chance you'll end up pretty sweet. AND DON"T FORGET THOSE RICE HULLS! At 20% Rye, it's going to be a tough mash, I'd even go more than 1 pound in it... The Flaked Rye is just another way to ensure you don't get a stuck mash.