I have had & do have stacked drillings on diamond core, C & C2, also bomb cores, & have not had a problem with roll out. None of mine are 3 3/8 stacked, & maybe those high flaring layouts are the ones that create that problem. I haven't experienced any bad roll, lack of hit, or burn out on any of mine, only problems being operator error!
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Wayne
FOS HARD CORE MEMBER
Bomb Squad & Diamond Cutter
Romans 14:11 Every knee shall bow