I had to disappear for a bit after that whole wedding cake event - I was burnt out! But now I'm making an anniversary cake for that bride's mom (so that one is also a "whatever you'd like to make" cake - yes!! ) and a friend from out of state called to see if I'd make their 25th anniversary cake - only he's the opposite of the bride... he knows exactly what he wants and will be sending me a pic from taste of home with a tiered gift cake. I have the sbs system - but it's for round cakes. Can I use it for square cakes? This is going to be another scary cake.

You could (with square boards under the cake), or you could order square plates:
https://www.bakerycrafts.com/Catalog.aspx?WebTab=WEDDING&TabCategory=WPLATES&ItemType=

I apologize for such an obvious question! I don't remember seeing the square plates before - I'm so glad! Thank you for pointing them out.