mainshafts better be within say 0,015mm, run out.
And more: one who has done a rebuild without checking the alignment of main bearings in the casings: oh, oh, oh.....
(not saying it happend here)
balancefactor i have by experience 52-54% but more important is the weight of the conrods to be the same, when doing my B crank i milled 0,8 mm form a to thick conrod, to make them both the same, its the most vibrationless bike i have now.
.
I saw the formula in Tuning For Speet
and when weighing the smallends, a big difference is seen measured when one does not have the centers LEVEL.
and even than; two ways: fist one read out when yust laying it on.
than when laying it on with bit presure and read when released.
cheers