Has anyone ever tried to put the hole in the cake before putting it on the cake?
For example, the bottom tier is 10" on the bottom, 11" in the middle and 12" on the top ------- then the middle tier (8" on the bottom) which sits inside of the top of the bottom tier.
I don't know if this is making sense.
I don't know if I'm gettin' what you're sayin' or not. But, you'd have less chance of it breaking if you cut the hole out after that final layer is on there.
but....you can definitely fill and and assemble each tier....carve, cut out the hole then crumb coat