Vacume Diafram 74 260z to much for 72 carbs?

[Xargon321]

my vacume advance dont work on my 74 260 its retro fitted with 72 round tops, in the haynes manual it says that the 72 vac adv starts at 3.94 in Hg and the 74 vac adv starts 11.8 in Hg now can the 72 carb pull that vacume should i change the diafram to a 72??