I'm planning a 12, 9 & 6" stacked. Will 1/2" foam core board be enough support?
should be, i would double it only because i like the look of a nice thick board under my cakes.
I know doubled it will support with out any problems.
Yes, I use the 1/2" foamboard all the time--not doubled. Plenty strong enough for that size of cake. I even use it on 16" cakes, 1/2 sheet cakes (2-layer). That way when I dowell, it goes all the way thru the foamboard and nothing shifts.