I would forget about what the guys numbers were with the GSC prop. As was already mentioned, one prop will be way different from another. For that mater, would you expect a 70" square tip warp to run the same pitch as a 70" taper tip warp prop? Of course not, and they are made by the same company but their shapes are different. Your main concern it your static rpm when you go to set it up. Most guys use about 6250 or even a bit less for static prop rpm. Once you are climbing out, you will likely see higher rpms as the prop unloads a bit from it's static setting. High EGTs are a killer on these 2 stroke engines. And in very short order as well. Not at all like a 4 stroke where maybe the valves start to burn after a while or something. But like maybe in one takeoff when you pull back to cruise rpm she quits. More prop load and or richer mixture = lower EGT temps. Two 582 manuals that I have say: Match propeller to achieve above indicated full load rpm. Indicated rpm was 6500 for 1 minute for the 582 with dual carbs and oil injection. Another thing to consider is the accuracy of the tachometer. Many of the analog tachometers are very inaccurate. A tiny tac is usually very accurate. Do some searches in the archives on any of this, and you will see I'm not the only one saying this. JImChuk