I have a question. I am making a groom's cake this weekend, and he just wanted it to be a single tier, so to make it the size he needed it to feed, I had to make 4 16" round cakes. My question is, when I stack them, do I need to put some sort of support in between like the second and third cake, or will it be fine to stack all four on top of each other. Thanks so much in advance for the advice.

It would give it a lot more support if you would put a cardboard round between the second and third layer and don't forget to dowel.

I agree I would also suggest using a plywood base and running a center dowell thru all layers to prevent slipping. HTH

Good advice above.

Basic rule is to use a support system for every 4" of cake height.