AI have read through all the threads on topsy turvies, and I think I have confused myself. I am planning a 3 tier for this weekend, for my sons 1st birthday (so not a paying customer). I am not to concerned about serving numbers, I already know there will way too much cake but I am more interested in adding it to my portfolio. I plan to start with 6, 8 and 10 inch round cakes. from there I am going to carve the tops (they will be 4" tall to start with and I will flip the top). I think I will also hollow out the top for the next tier to sit in. my real question comes from the sides. I plan to carve these to taper in, but I am unsure of how far. if the top tier has a top diameter of 6" is a base diameter of 5" enough of a slope for the tapering? that will also give me difference of 3" between the base of the top tier and top of the middle tier. I believe from reading through all the posts that a 3" difference is recommended? I thought maybe 6" down to 4" but then I was worried it might be too unstable (I plan to give him the top tier as his smash cake). hope you guys can help me clear up my confusion :)

On the topsy turvy that I made, I carved a 2" difference top to bottom.  With a 6" cake you only carve an inch and half difference to maintain the stability of the cake.   

To maintain the correct dimensions use a two inch smaller cake board for the bottom and use them as guides.  Such as for an 8" diameter cake use an 8" cake board on top and a 6" cake board centered on the bottom.  Carve the difference away with the bottom board up then turn over when you are finished carving.  It will make the carving much easier.

HTH.