I just got my Graphene Speed Pro and had it initially strung wuth a full bed of Tonic+ natural gut at 58 pounds. That was my setup for the IG Speed 315 I was using before. I've found that the Graphene Speed Pro really requires lower tensions because of the denser pattern. I love the feel of the gut but 58 is too high. I will try 55 next time. I have to use natural gut because of tennis elbow. No probs with the stiffer GSP.
Head Graphene Speed Pro | Babolat Tonic+ 16 @55 lbs