My initial thought would be no, but I'm not sure with that low of a gravity. My last stout was a breakfast style stout, and I cold steeped 4 lb chocolate malt, 3 lb roasted barley, and a pound of black patent. The gravity of this beer was 1.080ish and was an 11 gallon batch. The beer is stellar. My rule of thumb that I go by when cold steeping grains is to double the amount that you would mash. I have never used carafa II, so I'm not sure how roasty that tastes. But I would go out on a limb and say that this beer will have a very mild roastedness to it. I'm sensing that you want the rye to shine through some, so you don't want a heavy roastedness though. If it were me, I'd probably add a 1/2 pound to a pound of both dark grains to your bill.
See what anybody else has to say about this....
On a side note... I cold steep for roughly 24 hours in qt/lb of water