I am making a glass of Guinness for my step-dad's birthday in a couple of weeks. I was thinking of torting and filling each one and doing one 8" on the bottom, two 6" (or 7 if I go buy them) in the middle and two 8" on top. So my questions are: do I need to dowel each cake or just put cardboard under each cake? How do you make fondant stick going around, like so that it doesn't fall off from the top? I think that is all my questions for now. . .

Actually, I did try to plan such cake and unless you count the cakes with different heights, I am coming to slightly different numbers:

I did count each layer (meaning half of the cake "tier") as 2" high - on the bottom 6" tier, and on top of it one 8" tier, carved and one 8" tier. This should give you about 65 servings. Do you need a cake this big?

As for your question - stack it with dowels in the two bottom tiers, but also with a center dowel. Drive the center dowel in the cake board, if you can. The cake will be high and a bit top heavy.

And now for my drawing. I didn't draw the pillars and the cake board between the "tiers".

I forget your question about fondant. Crumb coat your cake. Roll the fondant as a wide strip, mist it with water and don't cover the cake from top, but roll this strip around the cake. Press it lightly to the sides and smooth it. Actually, you can cover first the topmost part of the cake with the "beer foam" and only after this cover the sides of your beer glass. It will be much easier and because you won't have heavy fondant pulling from top, less prone to tearing and similar problems.

Thank you so much for the responses! It is all so helpful! I don't really need one that big but there are always people to give the extra cake to. . . Plus, I have kinda been on this "go big or go home kick"! Also thanks for your response on the cake balls.

One idea to make it slightly less cake and perhaps even a bit easier - what about doing the bottom 6" cake a dummy? It gives about 15 servings less and because it is the bottom "tier", it is easier to make. The dummy would work as sort of cake stand for the top two tiers and you could drive a center dowel in this dummy tier. If you can get a 6" dummy easily, shave a bit from the sides to perfect the cake form (or if you won't destroy the cake dummy, make the form with royal icing and let it harden (going wider).

And good luck to you, whatever you decide.