I'm just trying to get my brain around this one. I need to re-create this cake (with red gerberas only). I would like to make the tiers closer to 5" high as they look taller than the standard 4". The cake needs to serve 50-55 and I would like to use a 4" for the top tier. What sizes would you go with? I'm thinking 4/6/9 but then it wouldn't be completely symmetrical. 4/6/8 wouldn't be enough and 4/6/8/10 would be too much. Any help would be appreciated!! Thanks!

Actually the 4, 6, 9 will be fine:)  You would need to make the 4 & 6"ers only 4" tall as they will appear taller.  The 9" could be a standard 4" also but probably would look more in line w/the others being 5" tall.