i dont know if i understand the question. are you asking what the maximum length pro taper is recommended with a 12mm tip size before the shaft gets too whippy and structurly unsound? if so, your probably better off in the "ask the cuemaker section" but just to throw a guess out there, i think the 314-2 has like 14"-15" taper and they don't recomend going below 12.25mm.