Ok I know its a MONSTER of a cake. Its a 5 tier square with an 18 inch base. I am a big fan of the SPS system but my question has to to with the fact the 18 inch base tier will be 6 inches tall! The others are 15,12,9,&6. Should I but a support in the middle of the 18 inch tier? So it doesn't sag? Also I can't refrigerate an 18 inch on the board so I was thinking about making 2 9x18's and putting it together just before transport. On top of it all I have to transport it 2 hours. Any suggestions would be appreciated:0

6 inches tall is not a problem. Just use the 9" legs cut to 6". There's no reason to put in extra support in the bottom tier. Why would it sag?

I think that square plates only come in even sizes, so you're going to have to use a 14" under that 15" tier. (Round plates come in all sizes.)

PS On Friday night I'm always in the FNCC thread on the Cake Decorating Forum.

Thanks! I appreciate the insigt.