the bulletin files says that the armor bulletins are not exclusive. like all other bulletins armor should stack too.
however it doesnt affect much, cause for example if ur likely to get penetrated 60% of the time, the armor bulletins will reduce that chance to maybe 58 or 57%.
the best bulletins to use i think are faster gaining veterency bulletins.
That's what i wanna figure out.
Try using armor bulletin on tanks that have high base armor.
ie: Panther with 4% more armor x3
320* 1.04^3 = 360
That's almost a IS2 right there