u may be ablle to get away with that, but i would deffinately not risk it,
i am also rebalancing a crank, i got new rods and pistons, the pistons are lighter than the old ones and the rods a lil heavier, i dont remember the actual amount of grams but it is very close
and i am still having it re ballanced to be safe
i mean u can think of it this way, 200 dollars to get it balanced give or take, more if they have to add metal.
or u can figure the cose of replacing the hole rotating assembly and possibly block if somethin goes wrong
jmo