I'm making a 4-tiered wedding cake and will be using the SPS method posted on the forum (which looks awesome, by the way!).
The tiers will be directly stacked on top of each other. The SPS instructions say that the method was designed for people who are traveling with the cakes, and it's been successful, but I'd like to hear some real-life experiences when traveling with already assembled, stacked cakes using the SPS method.
I keep having nightmares that the cake will topple over in my car on the way to the venue.. or that it'll start toppling and I'll try to catch it from falling by shoving my fingers into the cake/buttercream... the nightmare list goes on and on!
I've traveled with a stacked three tier a few times using the SPS and felt pretty confident about it. Of course I was careful driving but the thing just didn't budge at all. The person who wrote the SPS directions (Leah, I believe) uses it for all her cakes and I don't think she's ever had a problem so I'd consider it a pretty well tested system. Good luck and try not to worry too much!